Biology unit 2 topic 5

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Mitosis- involved in making normal body cells, required to rapair damaged tissue, grow, replace worn out tissue etc.
A cell divides by mitosis to produce 2 genetically identical cells with a full set of chromosomes (diploid nuclei). A copy of eah chromosome is made before the cell divides and lone of each chromosome goes into each new cell
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Meiosis
A cell divides by meiosis to produce 4 genetically non-identical cells,each with 1/2 original number of chromosomes.Before division a copy of each chromosome is made then divides twice to form gametes.Chromosome number is halved so for fertilisation
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Stem cells
unspecialised, found in human embryo & adult bone marrow. Can change into all different types of cell- can differentiate. Layer of cells in the embryo differentiate into all cells body needs. Cells in bone marrow can change into blood cells
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Mendel
Mendel was a monk who suggested the idea of separately inherited factors. Genes & chromosomes not known at time so not accepted. The ‘factors’ are now called genes
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DNA & stuff
Chromosomes are made of DNA – v.long molecule with double helix structure. Genes are short sections of DNA. Every individual (except twins) has different DNA. This unique DNA pattern can be used to identify people by their fingerprint.
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Inheritance in action
humans have 23 pairs of chromosomes. One pair being the sex chromosomes, females have (XX) chromosomes and males have (XY) chromosomes. Genes controlling the same characteristic are called alleles.
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Alleles
If an allele ‘masks’ the effect of another it is said to be dominant, if the allele is being ‘masked’ it is called recessive. Phenotype- physical appearance of the characteristic e.g-dimples. Genotype-which allele does individual inherit?e.g Dd or dd
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Homozygous & Heterozygous
Homozygous = both alleles are the same e.g DD (homozygous dominant) or dd ( homozygous recessive). Heterozygous= the two alleles are different e.g Dd
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Inherited conditions in humans
If allele is dominant, person only has to inherit one dominant allele to have genetic disorder e.g- polydactyly. If a parent is heterozygous for polydactyly each child 50% chance inheriting it.
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If allele is recessive, person must inherit two recessive alleles e.g- cystic fibrosis. Child must inherit recessive allel from both parents, can be passed on from two parents that don’t have it – called carriers of the allele.
If both parents heterozygous for cystic fibrosis, each child has a 25% chance of inheriting the disorder.
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Stem cells science & ethics
adult stem cells useful for treating disorders (leukaemia). Embryonic stem cells could be used to grow new tissues and organs for transplant. People think unethical as could be life
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Card 2

Front

A cell divides by meiosis to produce 4 genetically non-identical cells,each with 1/2 original number of chromosomes.Before division a copy of each chromosome is made then divides twice to form gametes.Chromosome number is halved so for fertilisation

Back

Meiosis

Card 3

Front

unspecialised, found in human embryo & adult bone marrow. Can change into all different types of cell- can differentiate. Layer of cells in the embryo differentiate into all cells body needs. Cells in bone marrow can change into blood cells

Back

Preview of the back of card 3

Card 4

Front

Mendel was a monk who suggested the idea of separately inherited factors. Genes & chromosomes not known at time so not accepted. The ‘factors’ are now called genes

Back

Preview of the back of card 4

Card 5

Front

Chromosomes are made of DNA – v.long molecule with double helix structure. Genes are short sections of DNA. Every individual (except twins) has different DNA. This unique DNA pattern can be used to identify people by their fingerprint.

Back

Preview of the back of card 5
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