Variation and inheritance Flashcards
What can be inherited?
Some human characteristics, such as facial features, can be inherited. They can be dominant or recessive.
What are alleles?
Alleles are different versions of the same gene.
What is the ‘nature or nurture’ debate?
There is a debate over how much ‘nature or nurture’. If genetic or environmental affect intelligence, sporting ability and health.
What are dominant and recessive characteristics depend on?
Dominant and recessive characteristics depend on dominant and recessive alleles.
When are dominant and recessive alleles expressed?
Dominant alleles are expressed when present but recessive alleles are expressed only in the absence of the dominant allele.
Number of Chromosomes
Most body cells have the same number of chromosomes. The number depends on the species of organisms. Human cells have 23 pairs.
How do sex chromosomes determine sex in mammals?
Females have identical sex chromosomes called XX, males have different sex cells called XY.
Which sex chromosomes do sperm carry?
X or Y chromosome
What sex chromosome does the egg cell carry?
X chromosome
Why is there an equal chance of offspring being male or female?
There is a random chance of which sperm fertilises an egg. There is therefore an equal chance of the offspring being male or female.
Genetic variation is caused by:
- 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.
What does homozygous mean?
Homozygous means having identical alleles.
What does heterozygous mean?
Heterozygous means having different alleles.
What is a genotype?
A person’s genotype is their genetic make-up.
What is a phenotype?
Their phonotype is which alleles are expressed.
