biology unit 2 - area of study 1
🇬🇧
In Inglés
In Inglés
Practique preguntas conocidas
Manténgase al día con sus preguntas pendientes
Completa 5 preguntas para habilitar la práctica
Exámenes
Examen: pon a prueba tus habilidades
Pon a prueba tus habilidades en el modo de examen
Aprenda nuevas preguntas
Modos dinámicos
InteligenteMezcla inteligente de todos los modos
PersonalizadoUtilice la configuración para ponderar los modos dinámicos
Modo manual [beta]
Seleccione sus propios tipos de preguntas y respuestas
Modos específicos
Aprende con fichas
Completa la oración
Escuchar y deletrearOrtografía: escribe lo que escuchas
elección múltipleModo de elección múltiple
Expresión oralResponde con voz
Expresión oral y comprensión auditivaPractica la pronunciación
EscrituraModo de solo escritura
biology unit 2 - area of study 1 - Marcador
biology unit 2 - area of study 1 - Detalles
Niveles:
Preguntas:
295 preguntas
| 🇬🇧 | 🇬🇧 |
| What are chromosomes | -Structure containing single DNA molecule and associated proteins - they carry genes |
| What do chromosomes look like | Various shapes and sizes – appearance changes over life of organism - when condensed they are depicted as long oval shapes - when uncondensed they are just floating strings |
| What types of chromosomes do eukaryotic cells have | Linear chromosomes |
| What does each chromosome possess | Each chromosome has a set of genes – passed on to daughter cells in mitosis and germ cell in meiosis |
| What chromosomes do prokaryotes have | Prokaryotes have a single circular chromosome – may also contain small circular DNA called plasmids which can move between cells |
| What is histone proteins | Histone proteins are the substance that DNA is wrapped around |
| What is a nucleosome | They are sections of DNA which is wrapped around histone proteins nucleosomes are particles, so they give DNA the appearance of string beads |
| What is the main function of nucleosomes | Serve to package DNA efficiently and protect it from enzymatic degradation |
| What happens to nucleosomes when chromosomes are condensed | When chromosomes are condensed nucleosomes fold producing supercoils |
| What is a centromere | Chromosomes have a constriction point called a centromere which divides the chromosome in to two sections called chromosome arms |
| What are chromosome arms | They are the two sides of a chromosome separated by a centromere |
| What are the names for the two types of chromosome arms | The shorter arm is the p arm and the longer the q arm – p arm is always on top |
| What are the names for the four positions centromeres can be in | Metacentric, submetacentric, acrocentric and telocentric |
| Where is the centromere if a chromosome is metacentric | Centromere is in the centre - p and q are equal |
| Where is the centromere if a chromosome is submetacentric | Centromere closer to one side making q almost double the length of p |
| Where is the centromere if the chromosome acrocentric | Centromere is very close to one end |
| Where is the centromere is the chromosome is telocentric | Centromere is at the tip of the arm |
| How many genes does each DNA molecule have | Each DNA molecule has many genes |
| What is a locus | Each gene has a particular position called a locus on a specific chromosome |
| What is spacer DNA and what does it do | - Genes of each DNA molecule are separated by regions called spacer DNA → spacer DNA doesn’t code for a protein product → they space genes far enough apart that it enables enzymes and other molecules to interact with genes easily |
| What is a ploidy level | The number of sets of chromosomes in a cell |
| What is gametes ploidy level and how many sets of chromosomes do they have | Gametes have one set of chromosomes and are haploid (n) |
| What are somatic cells ploidy level and how many sets of chromosomes do they have | Somatic cells are diploid (2n) – two sets of chromosomes (1 from each parent) -> Humans have a diploid number of 46 |
| What are homologous chromosomes | Two chromosomes in a matching pair - have the same genes found in the same location -> same genes but different DNA (different variations of each gene - one maternal and one paternal) |
| What are sister chromatids | They are two chromosomes that are genetically identical and are created when DNA is duplicated |
| What are sex chromosomes | Chromosomes involved in the determination of a person’s sex |
| What are allosomes | Sex chromosomes |
| What is an autosome | Chromosomes not involved in sex determination |
| What are mating types | Some organisms (fungi and algae) don’t have allosomes and therefore don’t have sexes instead they have mating types |
| What are organisms called is they have two similar allosomes | Individuals with two similar allosomes are of the homogametic sex |
| What are organisms called is they have two different allosomes | Individuals with 2 different allosomes are of the heterogametic sex |
| What is haplodiploidy | In some species sex is determined by haplodiploidy – males develop from unfertilised eggs so are haploid and females are derived from fertilised eggs hence they are diploid (bees and wasps) |
| What are some environmental factors that can determine a species sex | Some species sex is determined by environmental factors such as temperature (turtles and crocodiles), day length (some types of shrimp) or richness and availability of food resources (types of worms) → when sea turtles lay their eggs if the temperature is between 32 and 34 degrees there will only be females but if the temp is between 26 and 18 degrees, they will all be male |
| What is chromosome banding | Chromosome banding refers to alternating light and dark regions along the length of a chromosome, produced after staining with a dye. A band is defined as the part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter |
| What are banding types used for | Banding types are specific and consistent in each species hence they can be used to distinguish between chromosomes and to identify changes in chromosome structure which may be associated with genetic abnormality |
| What is a karyotype | A karyotype is the image or picture of the full set of chromosomes from an organism’s cell – represented by chromosomes arranged in pairs according to length and centromere position |
| What are karyotypes used for | Karyotypes allow scientists to compare chromosomes of related species and allows them to identify changes associated with genetic abnormalities such as changes in chromosome number or structure |
| What is the human karyotype | The human karyotype is made up of 22 pairs of autosomes and 1 set of allosomes → the autosomes are numbered 1-22 and are order largest to smallest → allosomes are usually shown after autosomes |
| Give a brief description of a somatic cell | Somatic cells or body cells are diploid and undergo mitosis |
| Give a brief description of a gamete | Gametes or sex cells are haploid cells that are created when a diploid cell undergoes meiosis forming 4 haploid gametes |
| What form of reproduction is mitosis | Asexual reproduction |
| Do all somatic cells divide | No, some differentiate becoming specialised and lose their ability to divide |
| What are the four stages of mitosis | Prophase, metaphase, anaphase, and telophase – followed by cytokinesis |
| How long overall does mitosis take | Around 1 hour |
| What occurs in the first stage of mitosis | The first stage is prophase → nuclear division begins (the nucleus begins to split in two) – nuclear membrane dissipates → chromosomes condense and become visible – appear as double stranded → the nucleolus shrinks (nucleolus produces and forms ribosomes – found in the nucleus) → centrioles move to opposite sides of the cell → spindle microtubules or fibres form between the two centrioles – spindle fibres are made of contractile proteins |
| What occurs in the second stage of mitosis | Metaphase is second and is the longest stage of mitosis (50% of the time) → chromosomes are fully condensed and are lined up along equator → each chromosome is attached to a spindle fibre and each chromatid is slowly being pulled to each pole with equal forces from each direction |
| What is the nucleolus | Nucleolus produces and forms ribosomes – found in the nucleus) |
| What are microtubules | They are contractile proteins |
| What is kinetochore | It is a protein that connect spindle fibres and chromosomes |
| What is the third stage of mitosis | Anaphase is the third and shortest phase only lasting a few minutes → centromere holding the two chromatid separates – each chromatid (now a single chromosome) begins moving to opposite poles by shortening microtubules (contractile proteins) |
| What occurs in the last stage of mitosis | Telophase is the last stage before cytokinesis → chromosomes arrive at the two poles and are grouped at each end of the cell → revert to extended fibres of chromatin and nuclear membrane forms around each group of chromosomes → spindle microtubules disassemble |
| What are the 2 main stages of the cell cycle | Interphase and M phase (mitosis and cytokinesis) |
| What are the stages of interphase | Interphase is broken in to three stages – gap 1 (G1), synthesis (S) and gap 2 (G2) |
| What happens in the first stage of interphase | G1 is the longest stage and takes around 8-10 hrs → in this stage the cell grows and makes proteins and organelles → if the cell is big enough at the end of the stage the cell will pass the restriction or check point and continue to the S phase |
| What is Gap 0 or G0 | Some cells such as nerve cells and differentiated tissue cells never leave G1 and don’t undergo mitosis – this is known as G0 stage |
| What occurs in the second stage of interphase | S phase is the second one in interphase and takes 6-8 hours → DNA is replicated, and centrioles are duplicated → it ends when the DNA in the cell has doubles – each chromosome is now made from two sister chromatids → chromosomes become visible at the start of M phase (mitosis and cytokinesis) – evidence for S phase |
| What is the last stage of interphase | G2 is the phase when the cell actively prepares for mitosis and takes 4-6 hours → period of high metabolic activity and lots of protein production (for histones and spindle fibres) → after the phase ends the cell goes through a second checkpoint to ensure all genetic material is doubled and the cell is big enough to undergo division |
| Where are the two checkpoints in the cell cycle and what do they check for | 1. after G1 - if the cell is big enough at the end of the stage the cell will pass the restriction or check point and continue to the S phase 2. after G2 - cell goes through a second checkpoint to ensure all genetic material is doubled and the cell is big enough to undergo division |
| What is cytokinesis | Division of cytoplasm and is the last stage before the cell becomes two and re-starts interphase |
| What is a cleavage furrow | A cleavage furrow appears at the equator of the cell before the cell splits in to two daughter cells |
| What can the daughter cells do after they are created | Daughter cells can either grow via cell enlargement, become specialised or continue to divide |
| What are some features dividing plant cells dont have but somatic cells do | Most dividing plant cells do not contain asters or centrioles |
| Where are new cells formed in the plant body | New cells are formed in specialised areas of the plant body called meristems – plants contain many meristems but there are four types |
| What are the four meristems of a plant | Apical meristem, young leaves, axillary meristems, and root meristems |
| Where are apical meristems | Growing tip or apex of the plant which divides causing the plant to grow |
| What are young leaves | They are a type of meristem and they demonstrate active growth |
| Where are axillary meristems | Buds of developing leaves or flowers form in the axils of plants (axils are the upward angle between the main stem and a leaf or branch) |
| What are root meristems | They are a place of active growth - growing tips of roots |
| Why cant cytokinesis occur in plants | Plant cells have a rigid cell wall so cytokinesis cannot constrict the cell membrane |
| What do plant cells do to divide instead of cytokinesis | Due to the rigid cell wall cytokinesis cannot constrict the cell membrane inwards so instead a new cell wall and membrane is grown along the cell plate (centre of the cell) |
| What is the importance of mitosis | Has two main purposes – growth and repair → also, important as it maintains the chromosome number of somatic cells -> Mitosis also is helpful as when a cell becomes too large and the surface area to volume ratio is too low so it has to divide which increase surface area to volume ratio and makes gas exchanged more efficient |
| Why is mitosis important for growth | → multicellular organisms are grown from a single fertilised egg which divides increasing cell number → during period of growth cell replacement is higher than cell death however as you grow older and stop growing cell replacement occurs at the same stage as cell death |
| Why is mitosis important for repair | Responsible for the repair and replacement of damaged cells allowing your body to heal from injuries such as broken bones and scrapes → some organisms can generate new body parts when they are lost – sea star |
| What are two genes that help control the cell cycle | Proto-onco genes tumour suppressor genes |
| What is the function of protol-onco genes | Proto-oncogenes promote cancer, produce proteins that stimulate cell division, inhibit cell differentiation, and decreases apoptosis - -> also triggers apoptosis when cells are faulty, dividing too often, tumourous etc |
| What is the function of tumour suppressor genes | They slow down cell division, help repair damaged DNA, and inform cells when they need to activate apoptosis |
| What are tumour suppressor and proto-onco genes | They are two genes that control the cell cycle and they work together to control the cell cycle and when one is damaged or silenced problems tend to arise |
| What is apoptosis | Apoptosis or programmed cell death is the deliberate death of healthy cells → natural feature of healthy tissue and cells are preprogramed to die |
| What happens when cell reproduction and cell death is unbalanced | Cell reproduction and death is usually balanced – if there is too much reproduction it can lead to tumours and if there is too much it can lead to neurodegenerative diseases |
| What is the function of apoptosis | Apoptosis is a form of self-defence as well as it killed cells with viruses, old cells, cells with DNA damage, cells of the immune system, and cancerous cells |
| What are three reasons otherwise healthy cells die via apoptosis | → not fully developed cells are killed – in the embryonic brain cells that are not incorporated into the brain network are killed via apoptosis → there are more than needed – it takes energy to keep extra cells alive so excess cells die via apoptosis → they have outlived their usefulness – foetuses have webbed toes and fingers and when this feature is no longer needed the cells connecting these extremities die via apoptosis – also when you recover from an illness any leftover immune cells that are not needed anymore die via apoptosis |
| What is syndactyly | Incomplete differentiation of toes or fingers is called syndactyly and is a result of a lack of apoptosis |
| What are the two signals to activate apoptosis | The mitochondrial pathway and the death receptor pathway |
| For what reason is the mitochondrial pathway activated | The mitochondrial pathway is a signal from inside the cell to activate apoptosis and begins when there is serious damage inside the cell (damaged DNA) |
| What are the four steps of cell death via the mitochondrial pathway | → first proteins on the outside of the mitochondria are activated breaking down the mitochondrial membrane → this causes an enzyme known as caspase to enter the nucleus and destroy the DNA → organelles other than the nucleus and mitochondria are preserved as the cell is broken down into small fragments which are enclosed by a membrane → fragments bind to phagocytes which engulf them |
| What is the death receptor pathway | The death receptor pathway is a signal from outside the cell to activate apoptosis – cells have death receptors on their membrane that receive the message to begin apoptosis – process occurs in 5 steps |
| What are the five steps of the death receptor pathway | → message is received, caspases are activated, contact to neighbouring cells is lost, and messages are sent to phagocytes → cells shrink and blebs (bumps) form of the outside of the cell → caspase enters the nucleus destroying all DNA → organelles other than the nucleus and mitochondria are preserved as the cell is broken down into small fragments which are enclosed by a membrane → fragments bind to phagocytes which engulf them |
| What are blebs | They are bumps on the outside of the cell which are caused by the onset of apoptosis via the death receptor pathway |
| What is caspase | Caspase is an enzyme that destroys DNA and it is used in apoptosis |
| What can too much apoptosis lead to | Too much apoptosis can lead to neurodegenerative diseases such as AD and PD |
| What can too little apoptosis lead to | Too little apoptosis can lead to the formation of cancer and can lead to autoimmune diseases |
| What is necrosis | Is a type of cell death that occurs when cells are damaged by chemical or mechanical trauma |
| What are the main two steps of necrosis | → first the plasma membrane is damaged so it can’t control what enters and exits the cell, chromatin clumps, organelles swell, and the mitochondria has a loosely clumped texture almost resembling tufts of wool → cell swells and bursts, spreading intracellular contents over nearby cells causing inflammation |
| What causes necrosis | Chemical or mechanical trauma |
| What is chemotherapy | Chemicals that inhibit mitosis and causes apoptosis – also blocks growth promoting signals |
| What are some side effects of chemotherapy | Side effects – also effects cells that divide fast such as hair follicles and cells in the digestive tract |
| What are the two types of chromosomal abnormalities or mutations | Numerical or structural |
| Define aneuploidy | It is when there is an abnormal number of chromosomes |