8.1 origins of genetic variation

Question 1

the three origins of genetic variation

Answer 1

-meiosis - crossing over and independent assortment
- mutation
= random fertilisation

Question 2

method of crossing over

Answer 2

1) homologous chromosomes line up next to each other (M1 prophase)
2) tangle at specific loci (chiasmata)
3) crossing over occurs and alleles are swapped
gene number and location is still the same but different allele combination

Question 3

independent assortment

Answer 3

each pair of homologous chromosomes is arranged randomly ad lines up independently.
daughter cells contain a different arrangement of chromosomes.
gametes carry the same genes but with different combination of alleles.

Question 4

how mutation cause genetic variation
by a point (gene) mutation

Answer 4

change in base sequences which changes polypeptide chain produces.
error occurs in DNA replication
change in structure of entire DNA by one different amino acid.

Question 5

chromosome mutation

Answer 5

change in number or structure of chromosomes
error occurs in cell division

Question 6

deletion mutation

Answer 6

a portion f chromosome is lost, involves the loss of genes, it is often lethal

Question 7

duplication mutation

Answer 7

a portion of chromosome is doubled so gene sequence repeats

Question 8

inversion mutation

Answer 8

a portion of chromosome is deleted then reattached in an inverted position. gene sequence is therefore reversed

Question 9

translocation mutation

Answer 9

a portion of chromosome is deleted and rejoins at a different point in the same chromosome or a different chromosome

Question 10

random fertalisation

Answer 10

fusion of two haploid gametes to form a diploid zygote.
meiosis results in two genetically distinct gametes, random fertalisation by egg and seprm will always generate different zygotes