Biology topic 8

Question 1

How can meiosis cause variation?

Answer 1

Crossing over- Homologous chromosomes align with each other, homologous portions of non-sister chromatids trade places
Independent assortment- During metaphase, random lining up of chromosome pairs

Question 2

Sources of variation

Answer 2

Meiosis
Random fertilisation
Mutations

Question 3

Gene (point) mutation

Answer 3

Miscopying of 1 or more nucleotides
Substitution, deletion, insertion
Changes protein made

Question 4

Chromosomal mutation (translocation)

Answer 4

Changes position of genes within chromosomes

Question 5

Chromosomal non-disjunction

Answer 5

Change in the number of chromosomes
An entire chromosome is lost or gained during meiosis

Question 6

Mono-hybrid inheritance

Answer 6

Inheritance of a single gene
2 alleles for a single gene- 1 from male and 1 from female

Question 7

Sex-linkage gene

Answer 7

Gene located on one of the sex chromosomes
(most located on the X chromosome)

Question 8

Female gamete

Answer 8

XX
Homogametic

Question 9

Male gamete

Answer 9

XY
Hereogametic
Men more likely to suffer from disorder because they only need 1 recessive allele for condition whereas women need 2

Question 10

Haemophilia

Answer 10

Blood cannot clot properly
X linked recessive condition

Question 11

Autosome

Answer 11

Non-sex chromosome
linked- genes on same chromosome
unlinked- genes on diff chromosomes

Question 12

Gene locus (loci)

Answer 12

Specific location on a gene on a chromosome

Question 13

Recombinants

Answer 13

New combinations of phenotypes that were not seen in the original parental phenotypes- shows crossing over has occurred

recombinant % = no. of recombinants/total x 100

The smaller the recombinant %, the closer they are on the chromosome, the less likely crossing over will occur

Question 14

Genetic drift

Answer 14

Completely due to chance
Alleles are passed on
Bigger impact on smaller population

Question 15

Population bottlenecks

Answer 15

Ecological event may reduce population sizes dramatically
Disasters are unselective- happen by chance
Small surviving populations are unlikely to be representative of original population
By chance alleles may be over-represented among survivors, some may be eliminated completely
Results in low genetic diversity

Question 16

Founder effect

Answer 16

Loss of genetic variation that occurs when a small number of individuals become isolated, forming a new population with allele frequencies not representative of the original population