lecture 1: variation and inheritance

Question 1

genome sequence

Answer 1

cell -> nucleus -> chromosomes -> DNA -> gene

Question 2

what is meiosis

Answer 2

cell division
Reproductive organs
Production of gametes
4 daughter cells
Diploid to haploid
Genetically different to parent cell (variation)

Question 3

Meiosis

Answer 3

1. DNA unravels and replicates so there are 2 copies of each chromosome called chromatids
2. DNA condenses to form double-armed chromosomes.
   These consist of 2 sister chromatids, joined in the middle by a centromere.

Question 4

Meiosis I

Answer 4

3. Chromosomes arrange themselves into homologous pairs
4. Homologous pairs are then separated, halving the chromosome number

Question 5

Meiosis II

Answer 5

5. The pairs of sister chromatids that make up each chromosome are separated (Centromere divides)
6. Four haploid cells genetically different from each other have been produced

Question 6

diploid

Answer 6

Normal human body cells have the diploid number (2n) of chromosomes.
Meaning each cell contains two of each chromosome (a pair)
One from mum and one from dad

Question 7

Haploid

Answer 7

Haploid is a single set of unpaired chromosomes
Sperm and eggs contain the haploid number of chromosomes

Question 8

what is variation ?

Question 9

types of alleles pairs

Answer 9

homozygous = alleles are the same
heterozygous = alleles are different
hemizygous = only one allele (e.g. XY)

Question 10

phenotype

Answer 10

An individual’s observable traits
(affected by the alleles that are inherited and sometimes the environment)
For example brown hair, blue eyes, blood type and height

Question 11

Genotype

Answer 11

The genetic constitution of an organism (the different alleles an organism has

Question 12

complete dominance

Answer 12

occurs when one allele completely masks the other

Question 13

Huntington’s disease

Answer 13

An autosomal dominant allele causes the disorder.
Excess of repeats (CAG) present in HTT gene

Question 14

Cystic Fibrosis

Answer 14

autosomal recessive disorder
Mutation in CFTR gene on chromosome 7

Question 15

Cystic fibrosis (a recessive genetic disease also caused by one gene)

Answer 15

Cystic fibrosis (a disorder which causes the production of thick mucus in the lungs) is caused by a single gene.
The disorder is autosomal (linked to a chromosome not sex chromosome)
This means the cystic fibrosis allele (f) is recessive over the normal (F) dominant allele