B2.7 Cell Division and Inheritance Flashcards
How does sexual reproduction give rise to variation?
Reproduction without the need for fertilisation.
How are inherited characteristics controlled?
Some controlled by a single gene.
Others controlled by a number of genes.
What is an allele?
A different form of a gene.
What is a dominant allele?
An allele which controls a characteristic when it is present on only one of the chromosomes in the pair.
What is a recessive allele?
An allele which controls the development of characteristics only if the dominant allele is not present.
Which molecule are chromosomes made from and what is its structure like?
DNA.
What is a gene?
A small section of DNA.
What does a gene contain?
The genetic code for a particular sequence of amino acids which makes a specific protein.
What does DNA fingerprinting tell us?
Each person had a unique DNA which can be used to identify individuals.
What are the female sex chromosomes?
XX.
What are the male sex chromosomes?
XY.
What is a mono-hybrid cross?
A cross(joining of gametes) between organisms which looks at only one allele at a time.
What does homozygous and heterozygous mean?
Homozygous means both alleles which code for a particular protein are the same - bb or BB.
Heteroxygous means alleles are different - Bb.
What does genotype mean?
A description of the alleles present.
What does phenotype mean?
A description of the observed characteristics eg brown hair.
What are genetic disorders?
Disorders which are inherited due to mutations in genes.
What is ‘polydactlyly’ ?
When a person is born with extra digits.
Fingers or toes.
How is polydactlyly inherited?
It is caused by a dominant allele and can be passed on by only one parent who has the disorder.
What is cystic fibrosis?
A disorder of cell membrane which makes patients produce more mucus than normal.
Particularly in the lungs.
How is cystic fibrosis inherited?
It is a recessive disorder so both parents must be carriers of the cystic fibrosis allele.
What does a ‘carrier’ mean?
Someone who has the allele for a disorder but does not have the disorder themselves.
Carriers can only be present in inherited disorders which are recessive.
How can you carry out screening for these disorders?
You can screen embryos for the allele of genetic disorders.
What is a genetic pedigree?
A diagram that shows who in a family have a genetic disorder are carriers and are normal.
What ideas did Mendal propose and why was this discovery not recognised until after his death?
They did not take him seriously and knew nothing about genes.
Which organism did Mendal carry out most of his research on?
He looked at pea plants.
