| What is a genome? | The entire DNA of an organism |
| What is a gene? (1) | A section of a molecules of DNA which codes for a protein |
| Where are chromosomes located? (1) | In the cell nucleus |
| Where are genes located? (1) | On chromosomes, in the cell nucleus |
| Describe the structure of DNA (3) | DNA is a double helix
Contains bases A,T, C,G
Sugar-phosphate backbone
Double stranded |
| What is the base pairing rule? | A + T, C +G
Apple in the Tree
Car in the Garage |
| How is the structure of RNA different to that of DNA? (2) | RNA is single stranded
RNA contains Uracil (U) instead of Thymine (T). |
| What are the two main stages of protein synthesis called? | Transcription & Translation |
| What is the role of mRNA in protein synthesis? | The gene in the DNA is transcribed to form mRNA, which can leave the nucleus and deliver the base-sequence to the ribosome for translation |
| What is the role of the ribosome in protein synthesis? | The ribosome is where translation of the gene from mRNA to a chain of amino acid occurs, with the sequence of the mRNA being read in codons, coding for one amino acid. |
| What is the role of tRNA in protein synthesis? | tRNA contains an anti-codon to the mRNA codon which are complementary. The tRNA delivers the correct Amino Acid to the chain of Amino acids forming in translation. |
| What are the roles of codons and anticodons in protein synthesis? | The mRNA contains codons, the tRNA anticodons which are complementary. This ensures that only the correct amino acid for coded in the sequence is added tot he resulting polypeptide. |
| How do we end up with differences in inherited characteristics? | There are different forms of any given gene called alleles. We inherit one allele from each parent, resulting in two copies of every gene. |
| Describe the stages of mitosis (5) | P - Prophase - preparation, chromosomes condense
M - Metaphase - middle, chromosomes line up across the middle of the cell
A - Anaphase - away, the sister chromatids are pulled away to opposite poles by their centromeres
T - Telophase - two, two nuclei are formed
C - Cytokinesis - the cytoplasm pinches and separates forming two separate cells |
| Which type of cell division results in two identical daughter cells? | Mitosis |
| List the reasons why a cell may divide by mitosis. (4) | Growth
Repair
Cloning
Asexual Reproduction |
| Which type of cell division results in four non-identical daughter cells? | Meiosis |
| Why would a cell a cell divide my meiosis and where in the body would this happen? | To produce gametes in the testes or ovary |
| Why does random fertilisation produce variation in offspring? | Every gamete is different so every combination will result in genetically different offspring |
| What is the haploid number of chromosomes in humans? | 23 |
| What is the diploid number of chromosomes in humans? | 46 |
| Are gametes diploid or haploid? | Haploid |
| Are body cells haploid or diploid? | Diploid |
| What are the two types of variation? | Genetic and Environmental |
| Mutations in which cell type will mean that it will be passed onto the next generation? | Gametes |
| How can a mutation affect the phenotype of an organism? | The sequence of amino acids is changed in a protein |
| How can a mutation result in a non-functioning enzyme? | The sequence of amino acids in the protein is changes, so does the 3D shape, resulting in an active site that can no longer fit the substrate. |
| Do most mutations have a significant effect? | No - most are silent mutations and do not affect the resulting protein.
(because the code is degenerate, multiple codons code for the same Amino Acid) |
| List as many mutagens as you can: | Ionising Radiation such as:
Gamma-rays
X-Rays
Ultraviolet Rays (sun exposure)
Chemical mutagens such as:
Cigarettes
Processed food |
