Genetic variation and genetic disorders and old and new species

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Genetic variation
Genetic variation
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Why does sexual reproduction lead to variation?
Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent.
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How many pairs of chromosomes are there in human body cells? female sex chromosomes? male sex chromosomes?
In human body cells, one of the 23 pairs of chromosomes carries the genes that determine the sex, females are the same (**) males different (XY)
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How many genes control the ability to roll your tongue? What is an allele
Some characteristics are controlled by a single gene. each gene may have different forms called alleles.
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What is a dominant allele?
An allele that controls the development of characteristics when it is present on only one of the chromosomes is a dominant allele
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what is a recessive allele?
An allele that controls the development of characteristics only if the dominant allele is not present is a recessive allele.
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what does DNA stand for? what is the structure of DNA called?
Chromosomes are made up of large molecules of DNA (Deoxyribonucleic acid) what has a double helix structure.
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What do genes code for?
Each gene codes for a particular combination of amino acids which make a specific protein.
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Each person (apart from.....) has unique DNA. this can be used to identify individuals in a process known as DNA .........?
Each person (apart from identical twins) has unique DNA, this can be used to identify individuals in a process known as DNA fingerprinting.
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Genetic Disorders
Genetic Disorders
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How do some people come to have cystic fibrosis?
Some disorders are inherited
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What is polydactyly? how is polydactyly inherited?
Polydactyly- having extra fingers or toes- is cause by a dominant allele of a gene and can therefore be passed on by only one parent who has the disorder
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What part of the cells is affected by cystic fibrosis? What is a carrier? What causes cystic fibrosis?
Cystic fibrosis (A disorder of cell membranes) must be inherited from both parents.. the parents may be carriers of the disorder without actually having the disorder themselves, caused by recessive allele.
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embryos can be.... for the...... that cause these and other genetic disorders
Embryos can be screened for the alleles that cause these and other genetic disorders.
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Old and new species
Old and new species
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What evidence is there of early life forms?
Evidence for early forms of life come from fossils
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What are fossils?
Fossils are the remains of organisms from years ago which are found in rocks
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Describe 4 ways in which fossils may have formed?
-From the hard parts of animals that don'y decay easily -From parts of organisms that have not decayed because some of the conditions for decay are absent - parts of organism are replaced by materials during decay-are preserved traces Eg. footprint
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Why are there so few early forms of life? what has Destroyed most of the traces of early life?
Many forms of early life were soft-bodied, which means that they have left few traces behind. what traces were have been mainly destroyed by geological activity.
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What can we learn from fossils?
We can learn how much or little different organisms have changed as life developed on earth.
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6 possible causes of extinction?
1-changes to the environment over geological time 2-New predators 3-new diseases 4-new, more successful competitors 5-a single catastrophic event 6-through the cyclical nature of specification
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2 ways new species are formed?
1-Isolation- 2 populations of a species become separated 2-genetic variation-each population has a wide range of alleles that control their characteristics
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Another 2 ways new species are formed?
Natural selection- In each population, the alleles that control the characteristics which help the organism to survive are selected. 2- Specification- the populations become so different that successful interbreeding is no longer possible.
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Other cards in this set

Card 2

Front

Why does sexual reproduction lead to variation?

Back

Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent.

Card 3

Front

How many pairs of chromosomes are there in human body cells? female sex chromosomes? male sex chromosomes?

Back

Preview of the front of card 3

Card 4

Front

How many genes control the ability to roll your tongue? What is an allele

Back

Preview of the front of card 4

Card 5

Front

What is a dominant allele?

Back

Preview of the front of card 5
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