Genes, Chromosomes, Genomes Flashcards
What is the central dogma of molecular biology?
there is a directional flow from DNA to protein via the messenger RNA (mRNA)
What is DNA transcribed to?
mRNA
What is mRNA translated to?
protein
What is gene expression?
process of going from DNA to protein
What is a codon?
triplets of bases that code for an amino acid
What are the three components to the chemical makeup of DNA?
Pentose sugar
Nucleotides
Phosphate groups
What are the pyrimidines?
Cytosine
Thymine
Uracil
What are the purines?
Adenine
Guanine
What is the difference betweeen pyrimidines and purines?
purines contain a sixmembered nitrogencontaining ring fused to an imidazole ring
whereas pyrimidines contain only a sixmembered nitrogencontaining ring
What makes a nucleoside?
base + sugar
What is a nucleotide?
monomer unit of DNA/RNA
base + sugar + phosphate group
What does a phosphodiester bond link?
Phosphate and sugar group for the sugar-phosphate backbone of DNA
What are combinations of base pairs?
G-C
A-T/U
How many hydrogen bonds between G-C bases?
3
How many hydrogen bonds can adenine form to another base?
2
Which bonds are stronge A-T or G-C?
G-C
What is hybridisation?
process of combining two complementary single-stranded DNA or RNA molecules
What is renaturation also reffered to as?
hybridisation
True or False?
Tm is the temp at which all the DNA has melted?
False
Tm is when half the DNA has melted
True or False?
Tm is lower in DNA with high G-C content
False
Tm is higher in DNA with high G-C content
True or False?
GC rich regions of DNA are more strongly bonded
True
True or False?
Repeats in DNA sequences lead to longer renaturation times
False
repeats hybridise faster because there are more copies
How much of the human genome is actually genes?
~25%
What percent of the human genome encodes for proteins?
~1.5%
What is an allele?
different forms of genes
What study found that genes lie on chromosomes?
1910
Thomas Hunt Morgan
Who found that Chromosomes contain genes in linear array?
19-13
Alfred Henry Sturtevant
What is most of the gene made of?
Introns and regulatory DNA sequences
What is a gene?
stretch of DNA that functions as a unit to give rise to either RNA or a protein
What is the sense strand also reffered to as?
The coding strand
What is the antisense strand also reffered to as?
The template strand
What happens to the sense strand?
Transcribed to RNA and then translated into a protein
Which strand is the coding strand?
The sense strand which can be either strand of the DNA strand
What does DNA having antiparallel strands result in?
the strand can be read either way to give different proteins
True or False?
A gene encodes one (or many) polypeptides or structural RNAs
True
True or False?
Genes on the same chromosome segregate independently
False
Genes on different chromosomes segregate independently genes on the same chromosome are said to be linked
True or False?
Most of the human genome is made up of gene sequences
False
Only ~25% of human genome is made of genes
True or False?
Most of the gene sequence is used to encode the protein
False
Mostly control sites and introns (in eukaryotes)
What are control sites?
provide binding sites for proteins
regulate gene expression
What are coding regions?
expressed via RNA synthesis
What are promoters and terminates?
Control regions
What does a promoter do?
Contain binding sites for transcription machinery (RNA polymerases)
Contain binding sites for regulatory factors that control when and where a gene is expressed
What does a terminator do?
Sites which signal when synthesis of mRNA should cease
Compared to prokaryotic genes in the control regions what extra parts do they have?
Enhancer regions
Compared to prokaryotic genes in the coding region what extra parts do they have?
introns and exons
What are exons?
Sequences that encode protein in the final/mature mRNA
What are introns
Sequences which break up the coding sequence
Need to be removed during maturation of mRNA
Few and small in simple organisms
More common and can be large in higher eukaryotes
What does splicing do?
removes introns and links the coding sequences found in exons
What flank the coding region to allow accurate splicing?
short donor and acceptor sites
What mediates splicing?
The spliceosome
What is snRNA?
small nuclear RNA
What is alternative splicing?
Different exons from a gene used to code for various proteins
True or False?
Control regions are expressed mRNA synthesis
False
Coding regions are expressed mRNA synthesis
True or False
Introns are sequences that encode the mature mRNA
False
Introns are spacer regions between exons
exons encode for mature mRNA
True or False?
Promoters are used to control gene expression and are found downstream of the coding region
False
Promoter regions are usually found upstream of coding region
True or False?
Alternative splicing is where different exons from the same coding region can be ligated to form alternative mRNAs leading to many different protein sequences
True
What is the genome?
The entire “library” of genetic instructions that an organism inherits
What is the functional unit of the genome?
the gene
How many base pairs in the human genome?
over 3 billion
How many base pairs in the E.coli genome?
4.6million
Do closely related species need to have similar number of chromosomes?
Nope
What is probably the minimum number of required genes for a viable cell?
200-300 genes
What is mycoplasma labatorium?
a simple synthetic organisms
created by Craig Venter
What is a metagenome?
The sequencing of the collective genomes of all microorganisms that exist within a particular environment
