(todo 3.8B) Reproduction, DNA and Protein Synthesis - Paper 1 Flashcards
(13 cards)
Explain advantages of sexual reproduction compared to asexual.
- Variation is present in the offspring.
- Humans can speed up natural selection through selective breeding.
Explain advantages of asexual reproduction compared to sexual.
- There is no need to find a mate.
- It is faster.
Explain the role of cell division by meiosis.
Meiosis produces 4 haploid daughter cells with half as many chromosomes as the diploid parent cell.
Describe the structure of DNA.
- DNA is a polymer.
- Two strands coil to form a double helix.
- Complementary base pairs connect the strands by weak hydrogen bonds.
- Each nucleotide has a base, a deoxyribose sugar and a phosphate group.
Define a genome.
A genome is the entire DNA of an organism.
Define gene
A gene is a section of a DNA molecule.
Explain how DNA can be extracted from kiwi.
- Peel the skin from half a kiwi fruit and mash it up.
- Mix a teaspoon of salt and small volume of washing up liquid into the fruit.
- Gently heat this mixture at about 60°C for five minutes.
- Filter the mixture and retain only the filtrate.
- Cool using an ice bath and gently pour chilled ethanol onto the top of the filtrate.
- You will see strands of DNA with bubbles in them at the boundary between the filtrate and the chilled ethanol.
Define codon
A codon is a triplet of bases.
How does the order of codons in a section of DNA produce specifically shaped proteins?
The order of the codons in a section of DNA decides the order of amino acids in the protein.
The amino acids fold to produce specifically shaped proteins.
What are the 2 key phases in protein synthesis?
Transcription and translation.
Describe the stages of transcription.
- The double helix structure of a section of DNA is unwound by helicase enzyme breaking the weak hydrogen bonds between the 2 strands.
- The enzyme RNA polymerase attaches to the DNA in a non-coding region just before the gene.
- RNA polymerase moves along the DNA strand. Free RNA nucleotides form hydrogen bonds with the exposed DNA strand nucleotides by complementary base pairing (U replaces T), forming a complementary copy.
Describe how genetic variants in the non-coding DNA of a gene can affect phenotype.
Some sequences of non-coding DNA are not as good at binding to RNA polymerase. This means the enzyme could be less likely to bind and so less protein is produced, which can affect phenotype.
Describe how genetic variants in the coding DNA of a gene can affect phenotype.
This alters the sequence of amino acids and therefore the activity of the protein produced, which can affect phenotype.
