Variation and inheritance Flashcards Preview

Biology GCSE OCR 1-3 > Variation and inheritance > Flashcards

Flashcards in Variation and inheritance Deck (17)
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1
Q

What can be inherited?

A

Some human characteristics, such as facial features, can be inherited. They can be dominant or recessive.

2
Q

What are alleles?

A

Alleles are different versions of the same gene.

3
Q

What is the ‘nature or nurture’ debate?

A

There is a debate over how much ‘nature or nurture’. If genetic or environmental affect intelligence, sporting ability and health.

4
Q

What are dominant and recessive characteristics depend on?

A

Dominant and recessive characteristics depend on dominant and recessive alleles.

5
Q

When are dominant and recessive alleles expressed?

A

Dominant alleles are expressed when present but recessive alleles are expressed only in the absence of the dominant allele.

6
Q

Number of Chromosomes

A

Most body cells have the same number of chromosomes. The number depends on the species of organisms. Human cells have 23 pairs.

7
Q

How do sex chromosomes determine sex in mammals?

A

Females have identical sex chromosomes called XX, males have different sex cells called XY.

8
Q

Which sex chromosomes do sperm carry?

A

X or Y chromosome

9
Q

What sex chromosome does the egg cell carry?

A

X chromosome

10
Q

Why is there an equal chance of offspring being male or female?

A

There is a random chance of which sperm fertilises an egg. There is therefore an equal chance of the offspring being male or female.

11
Q

Genetic variation is caused by:

A
  • Mutations, which are random changes in genes or chromosomes
  • Rearrangement of genes during the formation of gametes
  • Fertilisation, which results in a zygote with alleles from the father and mother.
12
Q

What does homozygous mean?

A

Homozygous means having identical alleles.

13
Q

What does heterozygous mean?

A

Heterozygous means having different alleles.

14
Q

What is a genotype?

A

A person’s genotype is their genetic make-up.

15
Q

What is a phenotype?

A

Their phonotype is which alleles are expressed.

16
Q

What are inherited disorders caused by?

A

Inherited disorders are caused by alleles most of which are recessive.

17
Q

Many personal and ethical issues are raised:

A
  • In deciding to have a genetic test (a positive result could alter lifestyle, career, insurance)
  • By knowing the risk of passing on an inherited disorder (whether to marry/have a family)