B1-2 Why can people look like their parents, siblings, but not be identical to them? Flashcards
How many pairs of chromosomes does a body cell contain?
23 pairs - making 46 chromosomes.
How many pairs of chromosomes does a sex cell contain?
Trick! There aren’t any pairs - sex cells only contain one copy of each chromosome. This makes only 23 chromosomes.
Do chromosomes in a pair carry the same genes in the same place?
Yes - however, there may be different versions of the genes called alleles.
How many alleles do most people have for a gene?
2 alleles for each gene
What does homozygous mean?
The person has same alleles for each gene
What does heterozygous mean?
The person has different alleles for each gene
What happens during sexual reproduction?
Genes from both parents in the sex cells come together and produce variation in the offspring - some characteristics from both the mother and father.
Can parents and children have similarities?
Yes of course, they share because of the combination of both the fathers and mothers alleles in the zygote.
Why may two different children from the same parents not look the same?
This is because they will inherit a different combination of genes/alleles - making them different.
What does it mean if someone has one/two dominant allele?
Means they will show that characteristic held by the dominant allele
What does it mean if someone has one recessive allele?
This characteristic will not show as there is still a dominant present
What does it mean if someone has two recessive allele?
The recessive characteristic will show as there are two alleles.
What sex chromosomes do males and females have?
XX (Females) and XY (Males)
What does the sex determining gene on the Y chromosome do? And what happens if the Y chromosome is absent?
SDR-Y triggers the development of androgen (and testes). If Y is not present, then ovaries are developed.
What can we use to work out the phenotype of someone?
Genetic diagrams such as Family trees and PUNNET SQUARES.
