Higher: Biology
Learning Cards for the entire SQA Higher Biology Course
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Higher: Biology - Marcador
Higher: Biology - Detalles
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| 🇬🇧 | 🇬🇧 |
| What type of molecule is DNA | Double stranded helix molecule |
| What is DNA made up of | Repeating units called nucleotides |
| What is each nucleotide composed of? | A phosphate deoxyribose sugar a base |
| What is the base pairing in DNA | Adenine with Thymine Guanine and Cytosine |
| What is the backbone of each DNA strand produced (held together) by | Strong sugar-phosphate bonds bonds between the deoxyribose sugar and the phosphate in each nucleotide |
| Where on the deoxyribose sugar is a sugar phosphate bond formed | Between the 3' carbon of the deoxyribose sugar of one nucleotide and the phosphate of that nucleotide attached to the 5' carbon above or below it on the strand |
| What is the bond between the DNA bases | Weak hydrogen bond |
| What is the base pairing on DNA | Adenine - Thymine Cytosine - Guanine |
| Why is DNA described as an antiparallel structure? | Strands run in opposite directions One strand runs from 3' to 5' and the other runs from 5' to 3' |
| Give examples of eukaryotic cells | Animal cells plant cells fungal cells |
| Describe where DNA is found in eukaryotic cells | Eukaryotes have linear chromosomes in the nucleus which are tightly coiled and packaged with associated proteins called histones. They also contain circular chromosomes in their mitochondria and chloroplasts |
| Why is yeast a special example of a eukaryote | Yeast cells also have plasmids |
| Give an example of a prokaryote | Bacterial cells |
| Where is the DNA of prokaryotic cells found? | Their DNA is found in the cytoplasm of the cell as a single circular chromosome and smaller circular plasmids |
| What must take place prior to cell division? | DNA must be replicated exactly by DNA polymerase to ensure each daughter cell receives all the needed genetic information to carry out its activities and functions. |
| Describe the DNA replication process in vivo (living cells) | DNA is unwound and hydrogen bonds between bases are broken to form two template strands The enzyme DNA polymerase needs primers to start replication. Primer allows DNA polymerase to add DNA nucleotides using complementary base pairing to the 3' deoxyribose end of the primer DNA polymerase can only add nucleotides in one direction (3' - 5') resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments. The fragments of DNA on the lagging strand are joined together by the enzyme ligase |
| What is a primer | A short strand of nucleotides which binds to the 3' end of the template DNA strand |
| What is PCR | Polymerase Chain Reaction An automated process that amplifies DNA using complementary primers for specific target sequences |
| What are practical applications of PCR | It can amplify DNA to help solve crimes, settle paternity suits and diagnose genetic disorders |
| What is a primer in PCR | Short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of the DNA to be amplified |
| What happens (vaguely)during the PCR process | There are repeated cycles of heating and cooling to amplify the DNA each cycle doubles the number of DNA molecules that are present |
| Describe in detail each stage of the PCR process | Double stranded DNA is heated to between 92-98 degrees celcius to separate the DNA strands (completely) DNA is then cooled to between 50 and 65 degrees celcius to allow primers to bind to target sequences It is then heated to between 70 and 80 degrees celcius for head tolerant DNA polymerase to replicate the region of DNA |
| What does Gene expression involve | The transcription and translation of DNA sequences so that proteins can be made |
| Do all of the genes in a cell code for making a protein? | No only a fraction of the genes in a cell are expressed |
| What three types of ribonucleic acid (RNA) do transcription and translation involve? | Messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA) |
| What is RNA | A single stranded molecule composed of RNA nucleotides containing ribose sugar, phosphate and one of four bases, C, G, A, U |
| Name the four bases found on an RNA molecule | Adenine uracil cytosine guanine |
| What is the function of mRNA | Carries a copy of the DNA code from the nucleus to the ribsome. it is trascribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm |
| What is each triplet of bases on an mRNA molecule called | A codon a codon codes for a specific amino acid |
| Describe the structure of a tRNA molecule | They fold due to complementary base pairing they have an anticodon at one end and an amino acid attachment site for a specific amino acid at the other end |
| What is the function of tRNA | They carry their specific amino acid to the ribosome |
| What is an anticodon | An exposed triplet of bases |
| What is the function of rRNA | Forms the ribosome alongside proteins |
| What is transcription | The first step in protein synthesis when information from DNA is copied into an RNA molecule, a processs which takes place in the nucleus |
| Describe the transcription process | Transcription begins when RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases free RNA nucleotides are attracted to the exposed DNA bases RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing. When the mRNA primary transcript is complete it breaks away from the DNA molecule which rewinds into its double helix again |
| What happens after a eukaryotic cell transcribes a protein coding gene in the nucleus | The primary mRNA transcript is processed by a process called RNA splicing |
| What does RNA splicing form | A mature mRNA transcript |
| What happens during rNA splicing | The introns of the primary transcript are removed as they are non coding regions the exons are joined together to form the mature transcript as they are coding regions the order of the exons are unchanged during splicing |
| Describe the process of translation | TrNA is involved in the translation of mRNA into a polypeptide at a ribosome tRNA molecules carrying a specific amino acid attached to the amino acid attachment site arrives at the ribosome translation begins at a start codon and ends at a stop codon anticodons bond to codons by complementary base pairing, translating the genetic code into a sequence of amino acids peptide bonds join the amino acids together Each tRNA then leaves the ribosome as the polypeptide is formed |
| What is meant by gene expression/ genes that are expressed | Genes that code for making a protein |
| Why can many different proteins be expressed from one gene | As a result of alternative RNA splicing different mature transcripts can be produced from the same primary transcript depending on which exons are retained |
| How are polypeptides formed from amino acids | By being linked together by peptide bonds |
| How do polypeptides become proteins | Polypeptide chains fold to form the three dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids |
| What does the shape of a protein determine | The function of the protein |
| What factors can influence gene expression? | Environmental factors |
| What is cellular differentiation? | A process by which a cell expresses certain genes to produce proteins which are characteristic for that type of cell |
| What are stem cells? | Unspecialised animal cells that can divide to self renew and/or differentiate |
| What two types of stem cells are there | Embryonic - from an embryo Tissue (adult) stem cells - from tissues |
| Why are embryonic stem cells pluripotent? | Cells in the very early embryo can differentiate into all the cell types that make up the organism All the genes in embryonic stem cells can be switched on, so they can differentiate into any cell type |
| What are tissue stem cells involved in? | The growth, repair and renewal of cells found in that tissue |
| Why are tissue stem cells multipotent? | They can differentiate into all the types of cell found in a particular tissue type |
| Name some therapeutic uses of stem cells | The repair of damaged and diseased organs or tissues such as the repair of corneas - damaged by chemical attack regeneration of damaged skin, producing a skin graft for burn victims bone marrow transplant to treat patients with blood cancer, eg leukemia |
| What must happen to stem cells from the embryo in order to be used for therapeutic purposes? | They can self renew under the right conditions in the lab for these purposes |
| What does stem cell research provide information on? | How cell processes such as cell growth, differentiation and gene regulation work. |
| What do research uses of stem cells involve? | Stem cells being used as model cells to study how diseases develop stem cells being used for drug testing |
| Why is use of embryonic stem cells an ethical issue? | Stem cells can offer effective treatments for disease and injury, however it involves the destruction of embryos |
| Define meristems | Regions of unspecialised cells which can divide to self renew and/or differentiate into many cell types |
| What is a genome of an organism | The organisms entire hereditary information encoded in DNA |
| What is a genome made up of | Genes (DNA sequences that code for protein) and other DNA sequences that do not code for proteins. |
| What does most of the eukaryotic genome consist of? | Non-coding sequences. |
| What is the function of other dna sequences that do not code for proteins in our genome | They regulate (control) transcription (production of mRNA) others are transcribed but never translated (not used for making proteins) |
| What are mutations | Random changes in the DNA that can result in no protein or an altered protein being synthesised |
| What are single gene mutations | Involve the alteration of a DNA nucleotide sequence as a result of the substitution, insertion or deletion of nucleotides |
| What is a substitution mutation | Occurs when one base is substituted for another. substitutions result in a change that only affects one codon |
| Name the three types of substitution mutations | Missense nonsense splice site |
| Describe a missense substitution mutation | Missense mutations result in one amino acid being changed for another. This may result in a non-functional protein or have little effect on the protein |
| Describe a nonsense substitution mutation | Nonsense mutations result in a premature stop codon beng produced which results in a shorter protein |
| Describe a splice site mutation | When there is a substitution mutation at a splice site and then some introns may be retained and some exons may not be included in the mature transcript |
| Describe frame shift mutations | Insertions or deletions result in frame shift mutations frame shift mutations cause all of the codons and all of the amino acids after the mutation to be changed, having a major effect on the structure of the protein |
| Describe a deletion mutation | When a deletion mutation occurs, one (or several) bases is deleted from the DNA molecule |
| Describe an insertion mutation | When an insertion mutation occurs, one (or several) bases is inserted into the DNA molecule |
| Are frameshift mutations more are less dangerous than substitution mutations | They are more detrimental than substitution mutations the whole base sequence after the mutation is changed |
| What are chromosomal structure mutations | Involve the number or sequence of genes on a chromosome being altered |
| Name the four types of chromosome changes | Deletion duplication translocation inversion |
| Are chromosomal structure mutations dangerous | The substantial changes in chromosome mutations often make them lethal |
| Describe deletion chromosome mutation | Where a section of a chromosome is removed |
| Describe inversion chromosome mutation | Where a section of a chromosome is reversed |
| Describe translocation | Where a section of a chromosome is added to a chromosome, not its homologous partner |
| Describe duplication chromosome mutation | Where a section of a chromosome is added from its homologous partner |
| How can gene duplication be beneficial | Gene duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein |
| What is evolution | Changes in organisms over generations as a result of genomic variations |
| What is natural selection | The non random increase in frequency of DNA sequences that increase survival and the non random reduction in the frequency of deleterious sequences |
| Why is natural selection non random | Only individuals with advantageous DNA sequences will survive (only a specific group survive, survivors are not picked randomly) |
| What are deleterious sequences | Harmful DNA base sequences |
| Describe the theory of natural selection | In each generation more offspring are produced than it is possible for the environment to support each individual in the offspring has to compete and struggle to survive in order to reproduce and pass on its genes every individual in a population displays slightly different phenotypes due to random mutations. The individuals that possess characteristics that are better adapted to their environment are most likely to survive these individuals have advantageous DNA sequences which are non randomly selected for The less beneficial DNA sequences are gradually removed from the population as individuals displaying these characteristics have a reduced survival rate and chance of reproducing. They have deleterious DNA sequences which are non randomly selected against. |
| What can be done to polygenic characteristics to display that they have continuous variation / normal distribution | They can be graphed and tend to show a bell shaped normal distribution this distribution indicates that there are fewer individuals with the more extreme measurement of the characteristic and many more with the average measurement of the characteristic |
| What can happen to a characteristic's distribution when a selection pressure acts on it | The distribution can be altered |
| Describe stabilising selection | An average phenotype is selected for and extremes of the phenotype range are selected against |
| Describe directional selection | One extreme of the phenotype range is selected for |
| Describe disruptive selection | Two or more phenotypes are selected for |
| What are the two types of gene transfer | Vertical and horizontal |
| Describe vertical gene transfer | Genes are transferred from parent to offspring as a result of sexual or asexual reproduction |
| Describe horizontal gene transfer | Where genes are transferred between individuals in the same generation |
| Is natural selection slower or faster in prokaryotes | Natural selection is more rapid in prokaryotes as they can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer |
| What is a species | A group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups |