Genes/Inheritance

Question 1

Whats hemizygous?

Answer 1

Only one copy of gene e.g. X linked

Question 2

What is it when two alleles of a gene are both expressed neither being dominant or recessive to other?

Answer 2

Codominance

Question 3

If something is rare in exam question can assume it is

Answer 3

Recessive

Question 4

Can you be homozygous dominant

Answer 4

Can be but unlikely, normally assume in exam that its heterozygous

Question 5

Define genotype, phenotype, inheritance (exam Q)

Answer 5

Geno - genetic makeup of an organism, with reference to a gene or the whole genome

Pheno - Observational characteristics of an individual defined by genotype and environment

Inheritance - Genetic characteristics transmitted from parents to offspring via alleles.

Question 6

What is it called if one gene is responsible for a phenotype? 2 genes? Given an example of a polygenic disease

Answer 6

Monogenic

Polygenic

Albinism

Question 7

How is albinism inherited? What does this mean for 2 albinos offspring? What is this phenomena called

Answer 7

2 genes 2 alleles, recessive manner
Means their offspring less likely to get albinism as two types of gene ‘compliment’ each other so you get normal phenotype

Question 8

If two genes are on the same chromosome they are said to be _______

Answer 8

Linked

Question 9

Do linked genes independently sort at meiosis? What if they are really far apart?

Answer 9

No. If really far apart then yes almost behave like separate genes (i.e more likely to cross-over to separate chromosomes, genes that are close together are more likely to stay on same chromosome, or both go to other chromosome).

Question 10

Why does polygenic inheritance not lead to 1:1:1:1 offspring if the 2 genes are on the same chromosome?

Answer 10

Because it depends how much cross-over occurs at meiosis to how much 2 of the 4 allele combinations occur.

Question 11

Are X-Linked dominant and recessive males both phenotypic?

Answer 11

Yes as only one X chromosome so no difference. Difference is when they pass on to daughters as X linked dominant males will give condition to all daughters, X linked recessive won’t necessarily.

Question 12

If you have a pedigree of two genes that are linked, and it shows a low rate of recombination ~10% of genes for example what could you say about the 2 genes?

Answer 12

They are closely linked therefore less likely to independently assort, more likely to travel together in meiosis and therefore less recombination.

Question 13

Define progeny?

Answer 13

Child of a gamete that has undergone recombination of genes

Question 14

When does crossing over occur in meiosis? When does random assortment occur?

Answer 14

Crossing over - prophase I

Random assortment - metaphase I