sex determination and asexual reproduction
- Created by: tia5sos
- Created on: 22-11-20 14:06
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- sex determination and asexual reproduction
- chromosomes control whether you are female of male
- During sexual reproduction, the male gamete fuses with the female gamete during fertilisation and the resulting cell has two copies of every chromosome.
- There are 23 pairs of chromosomes in every human body cell. The 23rd pair are labelled xy. These are sex chromosomes - they decide whether you turn out male or female.
- Males have an X and Y chromosome: XY, the Y chromosome causes male characteristics.
- Females have two X chromosomes: **, the lack of a Y chromosome causes female characteristics.
- Like other characteristics, sex is determined by a gene.
- The Y chromosome carries a gene which makes an embryo develop into a male as it grows. Females, who always have two X chromosomes, don't have this gene and so develop in a different way.
- Punnett squares
- 1, you can draw a genetic diagram to show the probability of a child being a boy or a girl.
- 2. genetic diagrams are often used to show the inheritance of individual alleles, but here one is being used to show how whole sex chromosomes are inherited.
- the parents' gametes are written along the top and left side of the diagram. The male parent has an X and a Y chromosome and the female parent has two X chromosomes
- Then the combinations of the alleles from both parents are written in the relevant box in the table, to give all the possible combinations in the offspring.
- There are two ** genotypes and two XY genotypes, so there is a 50% chance of having a boy or a girl. This means there is a 50:50 ratio of boys to girls.
- Then the combinations of the alleles from both parents are written in the relevant box in the table, to give all the possible combinations in the offspring.
- Asexual reproduction involves mitosis
- Asexual reproduction is another form of reproduction - it's different to sexual reproduction in several ways.
- 1. In asexual reproduction there's only one parent so the offspring are genetically identical to the parent.
- 2. Asexual reproduction happens by mitosis - an ordinary cell makes a new cell by dividing in two.
- 3. The new cell has exactly the same genetic information (i.e. genes) as the parent cell - it is called a clone.
- bacteria, some plants and some animals reproduce asexually.
- chickens, komodo dragons and strawberries are some examples.
- chromosomes control whether you are female of male
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