Topic 8: Genetics Flashcards Preview

A2 Biology > Topic 8: Genetics > Flashcards

Flashcards in Topic 8: Genetics Deck (28):
1

What are the sources of variation?

Meiosis, mutations and random fertilisation

2

How does meiosis cause variation?

Random assortment and crossing over

3

What is the change in chromosome number during meiosis?

Diploid to haploid

4

What is random assortment?

When the paternal and maternal chromosomes are sorted into gametes randomly so there are many new combinations of alleles

5

Explain crossing over

- Prophase 1
- Chromosomes line up into a tetrad
- Chromatids get so close they cross over to form a chiasma
- Chiasma breaks and sections of the chromosomes get switched

6

What is a tetrad?

A pair of chromosomes

7

What is a chiasma?

The structure formed when chromosomes cross over

8

What is a mutation?

A permanent change in the DNA

9

What are the three main types of mutations?

Point mutations, chromosomal mutations and chromosome mutations

10

What are the types of point mutations?

Substitution, deletion and insertion

11

What is a point mutation?

When one base or a small section of the DNA is miscopied

12

What is a substitution mutation?

When a base is swapped for another

13

What is an insertion mutation?

When a base is inserted

14

What is a deletion mutation?

When a base is deleted

15

What is a chromosomal mutation?

When the genes on a chromosome are moved

16

What is a chromosome mutation?

When a chromosome is either added or removed

17

Why does fertilisation introduce variation?

All gametes have a different combination of alleles
Which gametes fuse together is totally random

18

Define phenotype

Physical and chemical characteristics that make up the appearance of an organism

19

Define genotype

Genetic information

20

Define gene

Different segments of DNA coding for a particular protein

21

Define homologous

When a pair of autosomes have the same genes

22

Define alleles

Different variations of a gene

23

Define locus

The position of a gene on a chromosome

24

Define homozygous

When two alleles for a characteristic are the same

25

Define heterozygous

When two alleles for a characteristic are different

26

Define dominance

When a phenotype is expressed regardless of whether the alleles are homozygous or heterozygous

27

Define recessive

When a phenotype is only expressed if the alleles are homozygous

28

Define polygenic

Traits that are affected by multiple interacting genes