Chromosomes Flashcards
Are prokaryote chromosomes haploid or diploid?
haploid
Do prokaryotes have nucleosomes?
No
In eukaryotes, chromosomes are built from nucleoprotein particles called _______
nucleosomes
Why are eukaryotic genes bigger than prokaryotic genes?
Introns
In human genome, less than 2% encodes proteins. True or false?
True
Each human cell contains approx 2m of DNA packaged into ___ chromosomes
46
What are chromosomes made of?
Chromatin
What is chromatin composed of?
50% DNA, 50% protein
the main chromosomal proteins are histones. True or false?
True
What are the 5 different types of histone proteins?
H1, H2A, H2B, H3 and H4
Histones are acidic and have a negative charge. True or false?
False - they are basic and have a positive charge
How do histones bind to DNA?
DNA has a negative charge, histones have a positive charge so they attract
How many peptide chains does the nucleosome contain?
8
What is meant by “the nucleosome has an octameric structure”?
Two of each H2A, H2B, H3 and H4
What is the role of histone H1?
Helps to pack the nucleosome together
Nucleosomes pack together to form an 11nm fibre. True or false?
False - pack together to form a 30nm fibre - the Solenoid model
on a chromosome, what letter is given to the short arm?
p
on a chromosome what letter is given to the long arm?
q
After replication, the chromosome consists of two sister chromatids. What is the name given to the point at which the two chromatids join?
centromere
What are the ends of a chromosome called?
telomeres
What are chromosomes stained with to show their G banding pattern?
Giemsa
Chromosomes are classified according to the position of the centromere. True or false?
True
When the centromere is in the middle of the chromosome, what is the name given?
metacentric
When the centromere is offset from the middle what is the name given to the chromosome?
sub-metacentric
In a small chromosome, when the centromere is near the tip, what is the name given?
acrocentric
There are 46 pairs of chromosomes. True or false?
False - there are 23 pairs of chromosomes (23 from mother, 23 from father)
How many pairs of chromosomes are autosomes and how many are sex chromosomes?
22 pairs are autosomes and 1 pair are sex chromosomes
What is karyotyping?
Diagnostic typing of nuclear contents
In karyotyping, chromosomes are arranged in increasing size, meaning chromosome one is the smallest. True or false?
False - arranged in decreasing size therefore chromosome 1 is the biggest and has the most genes
Which has fewer genes, the X or the Y chromosome?
Y
What is the medical relevance of karyotyping?
It identifies chromosomal abnormalities
What are the abnormalities that chromosomes can have?
Structural (difficult to detect)
Numerical
What is meant by aneuploidy?
Abnormal number of chromosomes
How is karyotyping used in pre-natal diagnosis?
Some chromosomal abnormalities can be identified by amniocentesis
Down syndrome is a numerical aneuploidy known as ______
Trisomy 21
Those who have Down syndrome have ___ copies of chromosome 21 instead of 2
3
Incidence of having a child with Down Syndrome increases with age at which you have the baby. True or false?
True
Karyotyping cannot be used for the diagnosis of malignant tumours. True or false?
False
