-The fusion of a male and female gamete (sperm and egg/pollen and egg) -Offspring inherit features from both parents -Offspring are genetically different to each parent -Gametes are created by meiosis
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Explain what asexual reproduction involves?
-New cells formed by mitosis -Only one cell needed -Genetically identical cells produced -Plants and animals use this type of reproduction to make replacement cells -Bacteria and some plants produce offspring this way -Very quick and energy efficient
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What are the stages of meiosis?
1. Genetic information is duplicated 2. Chromosomes randomly align at the centre of the cell 3. The cell divides with the new cell containing one copy of each chromosome 4. The second division happens in the same way 5. 4 gametes are formed
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How do gametes differ from normal cells?
They contain 23 chromosomes rather than 46. They are genetically different from one another. They are formed by meiosis not mitosis
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What are the advantages of sexual reproduction?
-Produces variation in the offspring -If the environment changes, variation gives a survival advantage by natural selection -Natural selection can be sped up by humans in selective breeding to increase food production
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What are the advantages of asexual reproduction?
-Only one parent needed -More time and energy efficient as no need to find a mate -Faster than sexual reproduction -Many identical offspring can be produced when conditions are favourable
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Give two examples of organisms that can reproduce both asexually and sexually
Malarial parasites reproduce asexually in a human host but sexually in the mosquito. Many fungi reproduce asexually by spores but also sexually to give variation. Many plants make seeds sexually but also reproduce asexually by runners/bulb division
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Describe the structure of DNA
It's a polymer made from four different nucleotides called base pairs. Each nucleotide consists of a sugar and phosphate section with a base pair attached. They are A & T and C & G. It is a double helix
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What is a genome and what is the importance of understanding the human genome
The genome of an organism is it's entire genetic material. The human genome will allow genes linked to different diseases to be found. Can help understand inherited disorders. Used for tracing past migration patterns. Can be used for DNA profiling
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Explain how a gene codes for a protein
The gene is replicated in the nucleus & a template is made. This leaves the nucleus and binds to a ribosome where it is translated. Each codon (3 bases) has a carrier molecule that brings a specific amino acid. They bind to form a polypeptide chain
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What is a mutation?
A random change in an organisms DNA. Most don't alter the protein or make such small changes that its function is not affected. A few mutations can mean an altered protein is coded for, changing its shape making it harder for it to do its job
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What does genotype mean?
The alleles a person has for a specific characteristic e.g Bb
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What does phenotype mean?
The characteristic some displays as a result of their genotype (e.g. brown eyes)
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What does homozygous mean?
If a person's genotype has two of the same allele for a characteristic e.g. AA or aa
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What does heterozygous mean?
If a person's genotype has two different alleles e.g Aa
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What is polydactyl? Is it caused by a dominant or recessive allele?
-Causes extra fingers or toes -Caused by a dominant gene
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What is Cystic Fibrosis? Is it caused by a dominant or recessive allele?
-A disorder of cell membranes which causes mucus to clog in the lungs and pancreas tubes -Caused by a recessive gene
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Which chromosomes do you have if you are male, and which do you have if you're female?
Male has XY, heterozygous chromosomes. Female has **, homozygous chromosomes
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Other cards in this set
Card 2
Front
Explain what asexual reproduction involves?
Back
-New cells formed by mitosis -Only one cell needed -Genetically identical cells produced -Plants and animals use this type of reproduction to make replacement cells -Bacteria and some plants produce offspring this way -Very quick and energy efficient
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