Chapter 7A Flashcards
What structure does a molecule of DNA form?
Double helix
The double helix looks like a twisted ladder— what are the rungs of the base composed of?
Base pairs
The double helix looks like a twisted ladder— what are the sides of the ladder made of?
Sugar molecules and phosphate groups
What is each DNA strand composed of?
Nucleotides
What are the three components of a nucleotide?
- Sugar molecule
- Phosphate group
- Nitrogenous base
There are four nitrogenous bases that occur in DNA molecules. What are they?
Cytosine, Guanine, Adenine, and Thymine
What does Adenine pair with?
Thymine
What does Thymine pair with?
Adenine
What does Cytosine pair with?
Guanine
What does Guanine pair with?
Cytosine
What is a gene?
Sequence of nucleotides that code for a protein.
What is an allele?
A variant of a gene
What is the structure of a chromosome?
DNA wrapped around histone proteins
What is a centromere?
The region where the cells spindle fibres attach
What are sister chromatids?
Copies of DNA joined at the centromere
What are homologous chromosomes?
Pairs of chromosomes that are the same size with the same gene loci
Explain how homologous chromosomes are inherited.
One inherited from mum (maternal) one inherited from dad (paternal)
How many homologous chromosomes do we have?
We have 22 pairs and X/Y
What is a karyotype?
Visual representation of homologous chromosomes + X/Y
What is a key role of the karyotype?
Identify chromosomal abnormalities
What is aneuploidy?
When an organism possesses an incorrect number of chromosomes
When an organism possesses an incorrect number of chromosomes, what is this condition called?
Aneuploidy
Draw the equation of Monosomy
2n - 1
2n - 1 represents what chromosomal abnormality?
Monosomy
What is an example of Monosomy?
Turner Syndrome
Explain Turner Syndrome.
Only one X chromosome, no Y
Draw the equation of Trisomy.
2n + 1
The equation 2n + 1 represents what chromosomal abnormality?
Trisomy
Name two examples of trisomy.
Down syndrome, Klinefelter syndrome
Explain Down Syndrome.
Trisomy - extra copy of chromosome 21
Explain Klinefelter Syndrome.
Trisomy - extra X chromosome in males
Write an equation representing the chromosomal abnormality of tetrasomy.
2n + 2
2n + 2 represents what chromosomal abnormality?
Tetrasomy
Explain tetrasomy X
Tetrasomy - two extra copies of X chromosome
Explain the term “Polyploidy”
An organism with more than two sets of each chromosome
