Inheritance and Sex Determination

Flashcards covering key concepts from the lecture on inheritance, including homozygous and heterozygous alleles, Punnett squares, and sex determination.

How many chromosomes do gametes have?

23 chromosomes - haploid

How many chromosomes do you get from your mum?

23 chromosomes - haploid

How many cell divisions are there in meiosis?

2

How are sperm cells adapted for their function?

High numbers of mitochondria to provide energy and a tail for swimming

What do the prefixes ‘hetero’ and ‘homo’ mean?

'Homo' from the Greek homos which means ‘same’. 'Hetero' meaning opposite or different.

What is a characteristic?

Quality, trait or feature of an individual e.g hair colour, eye colour

What does the term ‘homozygous’ mean?

When the two alleles of a gene are the same. E.g. BB or bb

What does the term ‘heterozygous’ mean?

When the two alleles of a gene are different. E.g. Bb

What does probability mean?

How likely or what chance - normally a fraction or a % example: ¼ or 25%

What is a sex chromosome?

A type of chromosome that determines the sex of an organism.

What is the genotype of a female?

XX

What is the genotype of a male?

XY

What is the probability of sex determination?

The probability of getting a girl or a boy each time an embryo is fertilised is always 50%.

Why does a person usually inherit two alleles of each gene?

Because they inherit two different copies, one from each parent

A mouse will always have black fur if one or two black fur alleles are inherited. What word best describes the black fur allele?

Dominant

Some humans are albino (they have white nair ana pale skin). This condition is caused by a recessive allele. n. The other allele. N. causes pigment to be made. There are three possible combinations of these alleles: NN, Nn or nn. Which one of these combinations will an albino person have?

nn

Two non-albino parents can sometimes have an albino child. Which combination of alleles must the two parents have for this to happen?

NN, Nn

What is the genotype of a heterozygous fly?

Aa or aA

Why do vestigial-winged flies only have one genotype: aa?

Vestigial allele is recessive