DNA
State the symbols for the 4 DNA bases
A, T, C, G
Where is the p arm on a chromosome?
It is the short arm. p for petite.
A metacentric chromosome has the centromere positioned.......(where?)
centrally.
What is chromatin?
DNA + histone protein
What is an allele?
A version of a gene. e.g. B
Which bases are joined by hydrogen bonds?
A to T
C to G
Where is the telomere?
At the end of a chromosome.
What is a karyotype?
An image of all the chromosomes in a single cell. Chromosomes are then arranged with homologous pairs.
What is a nucleosome?
A section of DNA is wrapped around histone proteins.
What determines an individual's phenotype?
their genotype and the effect of the environment.
State the full names of the four DNA bases.
adenine
thymine
cytosine
guanine
Name the region at which two chromatids are joined.
Centromere
Describe the difference between an acrocentric and submetacentric chromosome shape.
Acrocentric has the centromere positioned closer to the end than a submetacentric chromosome.
What does it mean to say DNA is anti-parallel?
That each strand runs in an opposite direction.
Which DNA bases are joined by two hydrogen bonds?
adenine and thymine
If DNA is compared to a ladder, then the sides of the ladder are made of .........?
alternating sugar and phosphate groups
What is the locus?
The location of a gene on a chromosome.
What are homologous chromosomes?
Where do they come from in humans?
Homologous chromosomes are pairs of chromosomes.
One comes from your mother, and one from your father.
What do the numbers 5' and 3' on a DNA strand refer to?
- the direction/orientation of the DNA OR
- it is the numbering of the carbons in the sugar group
What is a genome?
The full set of genes found in an individual. (in a somatic diploid cell)
What is nondisjunction?
The failure of chromosomes to separate during cell division. (anaphase)
Describe a chromosome using the terms:
chromatid
centromere
telomere
sister chromatid
An X- shaped chromosome has two identical sides, each one being a sister chromatid. The chromatids are joined at the centromere. At the ends of the chromosome are regions called telomeres.
Name all four chromosome shapes.
metacentric
submetacentric
acrocentric
telocentric
Which bases are purines?
Which are pyrimidines?
Purines are adenine and guanine
(Rem: PURE AG)
Pyrimidines are cytosine and thymine.
What is the difference between the terms polygenic and multiple alleles?
- polygenic is a condition controlled by 2 or more genes.
- multiple alleles is when a particular gene has lots of different alleles e.g. human blood groups