Topic 8: Genetics

Question 1

What are the sources of variation?

Answer 1

Meiosis, mutations and random fertilisation

Question 2

How does meiosis cause variation?

Answer 2

Random assortment and crossing over

Question 3

What is the change in chromosome number during meiosis?

Answer 3

Diploid to haploid

Question 4

What is random assortment?

Answer 4

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

Question 5

Explain crossing over

Answer 5

• 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

Question 6

What is a tetrad?

Answer 6

A pair of chromosomes

Question 7

What is a chiasma?

Answer 7

The structure formed when chromosomes cross over

Question 8

What is a mutation?

Answer 8

A permanent change in the DNA

Question 9

What are the three main types of mutations?

Answer 9

Point mutations, chromosomal mutations and chromosome mutations

Question 10

What are the types of point mutations?

Answer 10

Substitution, deletion and insertion

Question 11

What is a point mutation?

Answer 11

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

Question 12

What is a substitution mutation?

Answer 12

When a base is swapped for another

Question 13

What is an insertion mutation?

Answer 13

When a base is inserted

Question 14

What is a deletion mutation?

Answer 14

When a base is deleted

Question 15

What is a chromosomal mutation?

Answer 15

When the genes on a chromosome are moved

Question 16

What is a chromosome mutation?

Answer 16

When a chromosome is either added or removed

Question 17

Why does fertilisation introduce variation?

Answer 17

All gametes have a different combination of alleles

Which gametes fuse together is totally random

Question 18

Define phenotype

Answer 18

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

Question 19

Define genotype

Answer 19

Genetic information

Question 20

Define gene

Answer 20

Different segments of DNA coding for a particular protein

Question 21

Define homologous

Answer 21

When a pair of autosomes have the same genes

Question 22

Define alleles

Answer 22

Different variations of a gene

Question 23

Define locus

Answer 23

The position of a gene on a chromosome

Question 24

Define homozygous

Answer 24

When two alleles for a characteristic are the same

Question 25

Define heterozygous

Answer 25

When two alleles for a characteristic are different

Question 26

Define dominance

Answer 26

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

Question 27

Define recessive

Answer 27

When a phenotype is only expressed if the alleles are homozygous

Question 28

Define polygenic

Answer 28

Traits that are affected by multiple interacting genes