Flashcards in MGD 2- Genes Deck (82)
What is a nucleoside?
Base + Sugar via beta-glycosidic bond
What is a nucleotide?
Base + Sugar + Phosphate, via phosphodiester bond
Name the sugar type in DNA:
Name the sugar type in RNA:
Which type of nucleic acid is single-stranded?
Name the base types present in RNA:
A, C, G, U
What is the conventional way to represent a DNA base sequence?
Top strand is 5' to 3', left to right
Why is the 5' end of DNA delta negative?
Due to the negative charges present on the phosphate group at physiological pH
Which ion(s) are necessary to stabilise the negative charges of the phosphate group in DNA?
What is the secondary structure of DNA?
Right-handed double helix
What is the distance (in angstroms) between stacking bases?
How many base pairs form 1 turn of the DNA double helix?
What is the diameter (in Angstroms) of the DNA double helix?
What RNA secondary structure can form?
What bond joins nucleotides in DNA?
3' to 5' Phosphodiester link
Name the purine bases of DNA:
Name the pyrimidine bases of DNA:
Name the pyrimidine bases of RNA:
How many rings does a purine base have?
How many rings does a pyrimidine base have?
Name 3 types of non-covalent interactions:
1- Electrostatic interactions
2- Hydrogen bonds
3- Van der Waals interactions
Describe the 3 steps from DNA to chromosome formation:
1) -ve DNA is wrapped around +ve histone octamers
2) Beads-on-a-string is coiled into Solenoid 30nm fiber
3) Solenoid associates with scaffolding proteins into a Chromosome
Which histones form a histone octamer?
2 x (H2A, H2B, H3, H4)
What is the name of the DNA which is not wrapped around histones in the beads-on-a-string formation?
What formation is the DNA in to form euchromatin?
What formation is the DNA in to form heterochromatin?
Solenoid 30nm fiber
How many chromosomes encode the entire human genome?
24 (22 autosomes plus X and Y)
How many chromosomes do humans have?
23 pairs of chromosomes = 46
What is the name given to the short arm of a chromosome?
What is the name given to the long arm of a chromosome?
Which enzyme is required for DNA elongation?
What enzyme drives the forward reaction of DNA replication?
Pyrophosphatase (Cleaves PPi into 2Pi)
Name the 4 enzymes required for DNA replication:
What enzyme forms the DNA replication 'bubble'?
DNA helicase, as it unwinds the DNA double helix
Which prime end of DNA can DNA polymerase elongate?
3' - OH
How does DNA polymerase elongate the 5' end of DNA?
Primase forms an RNA primer with a 3' end which DNA polymerase can elongate. The primer is later removed and replaced with DNA.
Which enzyme can seal the nick between okazaki fragments?
What is the role of mitosis?
Cellular division of somatic cells to produce 2 identical daughter cells, to allow growth, maintenance and repair.
Name the 5 stages of Mitosis:
What 2 events happen in prophase of mitosis?
1- Chromosomes condense
2- Nuclear membrane breaks down
What happens in Prometaphase?
Kinetochore spindle fibres attach to centromeres of chromosomes
What happens in Metaphase?
Chromosomes line up on equator of cell
What happens in Anaphase?
Spindle fibres contract, causing centromeres to divide and sister chromatids move apart towards the poles of the cell
What 4 events happens in Telophase?
1- Nuclear membrane reforms
2- Chromosomes decondense
3- Spindle fibers disappear
4- Cleavage furrow develops
Genetic make-up of an organism
Expression of the genotype - observable characteristics
Transcription unit, a section of DNA within a chromosome which contains the code for a protein, and associated sequences necessary for its expression.
Alternative version of a gene
If phenotypic trait is present in homozygotes and heterozygotes
If phenotypic trait is present only in homozygotes
If both alleles in a heterozygote contribute to the phenotype
If more than 1 gene is responsible for phenotype, a child of 2 affected parents can be unaffected
2 albino individuals can have an unaffected child. How?
Complementation - more than 1 gene is responsible for the phenotype.
Define incomplete penetrance:
When the presence of a particular allele results in a defined phenotype in some, but not in all.
How many DNA molecules is present in a "replicated" chromosome?
The complete set of genetic material in a haploid set of chromosomes
What are the 2 types of cell division?
Which type of cell division creates genetic diversity?
How does meiosis produce genetic diversity?
Crossing over of homologous chromosomes in Prophase 1
Independent segregation of chromosomes in Anaphase 1
In which phase of meiosis does independent assortment take place?
In which phase of meiosis does crossing over of homologous chromosomes occur?
What occurs in G1 of the cell cycle?
Cellular contents (excluding DNA) is replicated
What occurs in S stage of the cell cycle?
DNA synthesis and replication
What occurs in G2 of the cell cycle?
Double check of chromosomes for error, and makes repairs
How many chromatids are present in 1 tetrad in meiosis 1?
How many replicated chromosomes are present at the start of Meiosis, and how many are present at the end?
46 replicated chromosomes at the start
23 replicated chromosomes at the end
Terminally differentiated cells are locked in which stage of the cell cycle?
What is the result after meiosis of 1 oocyte (2n)?
1 egg cell precursor (n)
3 polar bodies
What is the result after meiosis of 1 spermatocyte (2n)?
4 sperm (n)
What is the equation to calculate recombination frequency?
(Number of recombinants / total progeny) x 100
If the recombination frequency is less than 50 percent, what can be inferred?
They are on the same chromosome
What pattern of inheritance does Sickle Cell disease follow?
Mating between 2 heterozygotes carrying an autosomal recessive disease gives what chance of having an affected child?
Which pattern of inheritance can skip generations?
A pedigree in which all generations are affected, and affects equally men and women most likely follows which pattern of inheritance?
Huntingdon's disease follows which pattern of inheritance?
Haemophilia A follows which pattern of inheritance?
Describe the individuals affected by an X-linked recessive disorder:
To make an identical copy of something
What do you need to carry out a PCR reaction?
- Taq. polymerase
- DNA to be copied
- DNA primers
How is a PCR reaction performed?
- DNA heated to 95'C = form ssDNA
- Cooled to 50'C = primers anneal to ssDNA
- Heat to 72'C = optimum temp for T. pol
- Repeat = exponential increase of target DNA