GENETIC CONTROL AND PROTEIN SYNTHESIS Flashcards
DNA and RNA are:
macromolecules that are polymers of nucleotides = polynucleotides
what is the structure of a nucleotide?
pentose sugar:
deoxyribose in DNA
ribose in RNA
phosphate group
nitrogen base
what are the 5 types of nitrogen bases
purine bases:
Adenine
Guanine
pyrimidine bases:
Thymine
Cytosine
Uracil
DNA contains which bases?
ATGC
RNA contains which bases?
AUGC
what is the structure of a DNA molecule?
DNA is a double stranded molecule of two helical polynucleotide chains containing deoxyribose sugars
what are the properties of a polynucleotide?
the chain is formed of a sugar phosphate backbone that nucleotides are linked to by phosphodiester bonds
what links two nitrogen bases together:
purine bases: adenine and guanine = two hydrogen bonds
pyrimidine bases: thymine, cytosine and uracil = three hydrogen bonds
what are the purine bases?
purine bases: two hydrogen bonds and 2 rings
Adenine
Guanine
what are the pyrimidine bases?
pyrimidine bases: three hydrogen bonds and 1 ring
Thymine
Cytosine
Uracil
the two strands are:
complementary to each other
what is the structure of chromosomes?
DNA is coiled and wrapped around Histone proteins forming chromatin
what is the role of Histone proteins?
protects DNA and prevents it from tangling in the nucleus
how does DNA replicate?
helicase enzyme unwinds and separates the two DNA strands
DNA polymerase forms a new strand by adding complementary bases from the old strand forming a new strand called the leading strand in a 5’ to 3’ direction
DNA polymerase forms another strand by adding complementary bases from the old strand in small sections called Okazaki fragments forming a new strand called the lagging strand in a 3’ to 5’ direction
Okazaki fragments are joined together by DNA ligase
why is replication semiconserative?
because each new DNA molecule consists of one new strand and one old strand
describe the experimental evidence supporting semiconservative replication
bacteria was put in 15N medium so that the DNA only contained 15N
a sample of the bacteria were put in a 14N medium and were allowed to grow and a sample was taken every hour
the samples DNA were extracted and put in a cesium chloride solution
it was found that the heavier the DNA, the closer it was to the bottom of the tube
what are telomeres?
regions of of repeated nucleotide sequences at the end of each chromatid
what are the roles of telomeres?
to protect the important genetic information from being lost during cell division
how many amino acids are in 1 base?
4 amino acids
what are the properties of RNA?
single stranded
has ribose sugar instead of deoxyribose
has uracil instead thymine
is shorter than DNA
what is mRNA?
it is made in the nucleus by the process of transcription
during transcription, the mRNA uses DNA as a template for complementary base pairing.
the DNA’s base triplets are converted into mRNA codons
the triple code TAC codes in to what codon?
AUG
1 codons code for how many amino acids?
1
what is tRNA?
each tRNA molecule has a sequence of 3 bases that are called anticodons and are complementary to codons on mRNA molecules.
each anticodon determines the type of amino acid
what is the anticodon for the codon AUG?
UAC
what is transcription?
the process in which DNA acts as a template to code for a strand of mRNA with complementary bases
what happens in transcription?
the enzyme helicase unwinds and separates the two DNA strands
RNA polymerase forms a sugar phosphate backbone holding the mRNA nucleotides
the mRNA, with its series of codons, leaves the nucleus through nuclear pores to the cytoplasm
the DNA rewinds into a double helix again
what happens in translation?
mRNA combines with a ribosome in the cytoplasm
tRNA molecules attach to the ribosome and their anticodons pair with the appropriate codons on the mRNA strand
tRNA have amino acids attached to them that bond to another amino acid on another tRNA molecule forming a peptide bond
the ribosome moves along the mRNA until it is exposed to a stop codon
what happens in translation?
mRNA combines with a ribosome in the cytoplasm
tRNA molecules attach to the ribosome and their anticodons pair with the appropriate codons on the mRNA strand
tRNA have amino acids attached to them that bond to another amino acid on another tRNA molecule forming a peptide bond
the ribosome moves along the mRNA until it is exposed to a stop codon
what is sickle cell anemia?
an inherited disease which results from a mutation in the gene coding for haemoglobin
what amino acid is different in a sickled cell anemia?
valine instead of glutamate
what type of mutation is sickle cell anemia?
single base substitution
