DNA, Genetics, Replication

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How is genetic variation achieved through meiosis? 2 ways.
- Independent assortment
- Crossing over
What is independent assortment?
- Various combinations of chromosomes are arranged
- During meiosis 1
- Homologous chromosomes line up in pairs
- Arrangement of pairs is random -> division into the daughter cells is random
What happens during crossing over?
- Pairs of chromosomes line up and exchange some of their genetic material.
- One chromosome may swap places with the same part of its homologous pair leading to a different combination of alleles on the gene
What are the stages of meiosis?
- Meiosis 1 - homologous chromosomes pair up, crossing over at the chiasmata may take place
- Cell divides, each daughter cell contains one chromosome from each homologous pair
- Meiosis 2 - chromatids of each chromosome are separated 4 haploid daughter cells produced
What happens during a substitution mutation?

A nucleotide base is replaced with another
What happens during a insertion mutation?
- An extra nucleotide base is inserted into the sequence
- Causes ‘frameshift’ -> all the subsequent bases are shifted down 1 place relative to the twin DNA strand
What happens during a deletion mutation?
- Absence of a nucleotide
- Causing ‘frameshift’ -> all the subsequent bases are shifted back 1 place relative to the twin DNA strand
Why may a DNA mutation be harmful?
- May result in change in order of bases
- Changes amino acid(s) coded for
- Final tertiary protein + its active site is deformed -> cannot fulfil function

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PassYourAlevels

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DNA, Genetics, Replication

Description

The genetics and DNA make-up of organisms, including replication and mutations.

Updated

2019-04-28T12:43:28Z

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