1. Meiosis and Genetic Variation Flashcards
Most cells in the body contain exactly the same genetic information except which cell?
The gametes - cells involved in sexual reproduction.
Define diploid.
When a cell contains 2 copies of each chromosome.
What do normal body cells contain?
Diploid number of chromosomes.
Meaning each cell contains 2 of each chromosomes, one from mum and one from dad.
What is the other way to write diploid number?
2n.
The chromosomes that make up each pair have what in common?
Same size and have the same genes.
BUT.
They could have different versions if those genes - alleles.
Define allele.
Alternative form of gene.
Define gene.
A section of DNA which codes for a protein.
What are pairs of matching chromosomes called?
Homologous pairs.
Define homologous pair.
A pair of matching chromosomes containing the same genes but could have different alleles.
How many homologous pairs of chromosomes do humans have?
23 pairs, so 46 chromosomes in total.
What is the diploid number for humans?
46.
Define gametes.
The sperm cells in males and egg cells in females.
Define haploid.
When a cell contains one copy of each chromosome.
How many chromosomes do gametes have?
Haploid number.
Only containing one copy of each chromosome in a homologous pair.
Haploid number is 23.
What is the other way to write haploid?
n.
What happens during sexual reproduction?
2 gametes join together at fertilisation to form a zygote, which divides and develops into a new organism.
At fertilisation…
A h.
Haploid sperm fuses with a haploid egg, making a cell with the normal diploid number of chromosomes.
Half the chromosomes come from father (sperm) half come from mother (egg).
How is fertilisation random?
Because any sperm can fertilise any egg.
Define zygote.
The diploid cell formed when 2 gametes fuse during fertilisation.
What does random fertilisation produce?
Zygotes with different combinations of chromosomes to both parents.
The mixing of genetic material in sexual reproduction increases genetic diversity within a species.
In humans, where does meiosis take place?
Ovaries and testes.
