B1h Flashcards
1
Q
how many chromosomes do humans have?
A
46 chromosomes, arranged in 23 pairs in the body cells. gametes only have 23 chromosomes
2
Q
what is XX and XY?
A
XX = female sex chromosomes XY = male sex chromosomes
3
Q
what is variation caused by?
A
- genes being mixed up when gametes are formed
- genes coming from 2 parents (fertilization)
- changes in genes or chromosomes called mutations
4
Q
what is an allele?
A
inherited characteristics are carried as pairs of alleles on pairs of chromosomes. different forms of a gene are different alleles.
5
Q
what are faulty genes responsible for?
A
inherited diseases such as sickle cell anemia and cystic fibrosis.
