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Terms in this set (51)
The transmission of genetic information from generation to generation
A thread-like structure of DNA carrying genetic information in the form of genes.
A length of DNA that codes for a protein
A version of a gene
What chromosomes does a man have?
What chromosomes does a Female have?
Describe the inheritance of Sex
It is determined by the chromosomes in the Sperm cell, as each female egg cell will have an X chromosome, however 50% of the sperm cell will have a Y chromosome and 50% will have an X chromosome. It is a 50% chance that either an X chromosome will fertilise the egg or a Y chromosome. If an X chromosome fertilises the egg then a female body develop or vice versa if Y, unless the gene to stimulate the development of testes is not there or there is a mutation in the egg of the Y chromosome.
What is DNA responsible for?
1. The development of specific proteins as the base sequences of DNA, making up a particular gene, are genetic code from the correct order of amino acids for making a particular protein.
2. Other types of proteins:
B. Receptors for neurotransmitters
What are the letters of the bases in DNA?
A, T, C, G
What are ribosomes?
Site of protein synthesis
How to make a protein?
1. MRNA arrives at the ribosomes from the nucleus carrying the base sequence for each particular amino acid in the protein.
2. As it passes through the Ribosome the amino acid is assembled into protein molecules.
3. Then the amino acids they bond together to form a long chain- protein.
4. The sequence of the amino acid is determined by the base sequence of the triplets carried by the MRNA.
5. The amino acids bond together by the peptide bonds.
Define haploid nucleus
A nucleus containing a single set of unpaired chromosomes e.g. In a gamete
Define diploid nucleus
A nucleus containing two sets of chromosomes.
What is inside a diploid cell?
A pair of each type of chromosome and in a human diploid cell there are 23 pairs.
Nuclear division giving rise to genetically identical cells
How does mitosis help in growth
Growth all over the body for humans and in special growing areas called MERISTEMS such as the root or stems for plants.
How does mitosis help in repair?
Skin cells divide to repair damaged tissues and wounds.
State the role of Mitosis in Growth, repair, replacement and asexual reproduction.
When does the exact duplication of chromosomes occur ?
What happens during Mitosis?
The copies of Chromosomes duplicate, maintaining the same number of Chromosomes.
Nuclear division giving rise to genetically different cells.
What is meiosis involved in?
The production of gametes.
Explain the term codominace
Codominance occurs when both alleles are expressed in the phenotype, neither allele is dominant over each other.
Why are both the alleles capital letters in codominance?
Because it shows that neither allele is dominant over the other and that both alleles aRE EXPRESSED IN THE PHENOTYPE.
What is the name given to the two plants crossed and the name given to the offspring they produce?
Parents= homozygous and offspring=hetrozygous
What is the name of the allele of blood groups
Ia, Ib, Io
What alleles are co-dominant in blood groups and what allele is recessive?
Ia and Ib and Io is recessive
What are the phenotypes of blood groups
A,B , AB, O
Define a sex-linked characteristic
A sex-linked characteristic is a characteristic where the gene responsible for the characteristic is located on a sex chromosome and therefore the characteristic is more common in one sex than the other.
Explain how being colour blind works?
There is a gene located on the X chromosome that is responsible for sight of the colours red and green. The gene works in the receptors, known as the cones in the retina. There however is an allele of this gene that does not produce the protein necessary for vision. This allele is recessive. If the mother has the alleles Rr she will have colour but because men have only one X chromosome, if they inherit the allele r they are colour blind.
The genetic make up of an organisms in terms of the alleles present
The observable features of an organism.
Having two different alleles for a particular gene
having two identical alleles of a particular gene
An allele that is expressed if present
An allele expressed when there is no dominant allele of the gene present
When two homozygous individuals breed together, if two heterozygous individuals breed together this is not pure-breeding
Differences between individuals of the same species
What is genetic variation
The differences in genotypes between individuals
What is phenotypic variation
The differences in the external and internal appearances of individuals.
What affects phenotypic variation
Environmental and genetic factors.
What does continuous variation result in?
A range of phenotypes between two extremes e.g. Height in humans.
What does discontinuous variation result in?
Limited number of phenotypes with no intermediate e.g. Tongue rolling
What is discontinuous variation caused by?
Mainly genes alone
What diagrams are used to present the data of continuous variation?
How is discontinuous variation data presented?
As a bar chart.
Define gene mutation
A change to the base sequence of DNA
What happens when genes mutate?
New alleles form
What increases the rate of mutation?
Some chemicals and ionising radiation
What are the symptoms of sickle cell anaemia
1. They can experience fatigue easily and get tired quickly
2. They can run out of breath easily
3. Leg Ulcers
4. Pain crises
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