B1 Variation and Inheritance mindmap
- Created by: Spanish
- Created on: 30-04-16 14:11
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- Variation and interheritance
- Inherited Characteritics
- Some human characteristic,such as facial features, can be inherited. They can be dominant or recessive
- Alleles are different versions of the same gene
- There is a debate over how much 'nature or nurture' (genetic or environmental factors) affect intelligence, sporting ability or health
- Dominant and recessive characteristics depend on dominant and recessive alleles
- Dominant alleles are expressed when present but recessive alleles are expressed only in the absence of the dominant allele
- Chromosomes
- Most body cells have the same number of chromosomes. The number depends on the species of organism.
- Human cells have 23 pairs
- Sex chromosomes determine sex in mammals. Females have identical sex chromosomes called **, males have different sex chromosomes called XY
- A sperm will carry either an X or a Y chromosome. All eggs will carry an X chromosome
- There is a random chance of which sperm fertilises an egg. There is therefore an equal chance of the offspring being male or female
- A sperm will carry either an X or a Y chromosome. All eggs will carry an X chromosome
- Sex chromosomes determine sex in mammals. Females have identical sex chromosomes called **, males have different sex chromosomes called XY
- Human cells have 23 pairs
- Most body cells have the same number of chromosomes. The number depends on the species of organism.
- Genetic variation
- A monohybrid cross
- A monohybrid cross involves only one pair of characteristics controlled by a single gene, one allele being dominant and one recessive
- Homozygous means having identical alleles, being heterozygous means having different alleles
- Inherited disorders
- Inherited disorders are caused by faulty genes
- Many personal and ethical issues are raised: in deciding to have a genetic test (a positive result could alter lifestyle, career, insurance), by knowing the risks of passing on an inherited disorder (whether to marry/ start a family)
- inherited disorders are caused by faulty alleles, most of which are recessive
- It is possible to predict the probability of inheriting such disorders by interpreting genetic diagrams
- Inherited Characteritics
- Genetic variation is caused by: Mutations, which are random changes in genes or chromosomes
- rearrangement of genes during the formation of gametes
- Fertilisation, which results in a zygote with alleles from the father and mother
- rearrangement of genes during the formation of gametes
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