Biology (genetics) Flashcards
What is a gametes?
A sex cell
At fertilisation…
A male gamete fuses with with a female gamete to produce a fertilised egg, also known as a zygote. The zygote ends up with the full set of chromosomes so it is diploid.
Meiosis-
A type of cell division. It’s different to mitosis because it doesn’t produce identical cells. In humans, meiosis only happens in the reproductive organs.
Polymers-
DNA strands are polymers. This means they’re made up of lots of repeating units joined together.
Proteins are polymers.
Each unit contains one of four different bases. A (adenine), T (thymine), C (cytosine), G (guanine)
A+T
C+G
Meiosis produces four haploid daughter cells.
.
The gamete-making cell has two sets of chromosomes. It is diploid.
The chromosomes replicate (and the copies stay stuck to one another)
The cell divided into two and then into two again. Each of the final four daughter cells has a copy of one chromosome from each pair. These are haploid.
Double helix-
A molecule of DNAcontains two strands, each which forms a shape called a helix. The two strands are joined together by pairs of substances called bases, to form a double helix.
Alleles-
Different forms of the same gene.
Homozygous-
If both alleles for one gene are the same.
Heterozygous-
If the alleles are different.
Sex chromosomes-
X+Y
XX= Females XY= Males.
Mutation-
A change in a gene that creates a new allele.
Genetic variation-
Caused by organisms having different alleles.
Environmental variation-
A change in the conditions in which organisms live.
