Ch 1 Lecture (Genes/DNA/RNA/Polypeptides) Flashcards
genome
Long sequence of DNA that provides the complete set of hereditary information for an organism
chromosome
A discrete unit of the genome carrying many genes
Consists of a very long molecule of duplex DNA and an equal mass of proteins
Is technically only visible during cell division
genetic recombination
The generation of new combinations of alleles in each generation
Usually produced by separate DNA molecules being joined into a single molecule due to crossing over or transposition
three parts of a nucleotide
- Pentose sugar
- Nitrogenous base
- Phosphate group
pentose sugar in DNA
deoxyribose
pentose sugar in RNA
ribose
on what carbon can we differentiate between deoxyribose and ribose
2’
purines
adenine
guanine
pyrimidine
cytosine
thymine
uracil
nucleoside composition
base
sugar
what carbon does the phosphate group attatch to?
5’
why is the phosphate important
negative charge
how are nucleotides connected to each other in one strand of DNA
phosphodiester bonds
how are DNA strands oriented
antiparallel
how are two strands of DNA linked together
hydrogen bonds
hydrogen bonds between A and T or U
2
how many bonds between C and G
3
two strands of DNA are not identical, they are
complementary
B DNA is how many base pairs per turn
10.5
supercoiling
The coiling of a closed duplex DNA in space so that it crosses over its own axis
Creates tension in the DNA molecule
supercoiling only occurs in
DNA with no free ends
positive supercoiling
DNA is twisted in the same direction as the helix
overwound
negative supercoiling
DNA is twisted in the opposite direction as the helix
pros of negative supercoiling
Creates tension that can be relieved by denaturing the helix
Promotes denaturing of helix
DNA replication is
semiconservative
semiconservative
Parental duplex separates
Each parental strand acts as a template for synthesis of a complementary daughter strand
who proved DNA replication was semiconservative
Meselson and Stahl
what separates parental strains
helicase
what synthesizes daughter strands
DNA polymerases
what relieves tension of supercoiling
gyrase
what is the point at which the parental strands are separated and replication occurs
replication fork
mutation
changes in the sequence of DNA
4 forces that alter changes in allelic frequency
selection
mutation
migration
drift
which of the 4 forces is the slowest
mutation
mutations can be induced by
mutagens
for a mutation to be passed down they must occur in,
gametes or germ cells
rate of mutation is balanced by
positive and negative mutations
a human infant has approximately how many new mutations
35
point mutation
changes a single base pair
point mutations can be caused by
chemical conversion or spontaneous errors
example of chemical conversion of base pairs
cytosine to uracil with nitrous acid
where is nitrous acid found
cured meats
which is more common, transition or transversion
transition
transition
replaces a purine with a purine or pyrimidine with a pyrimidine
transversion
replaces a purine with a pyrimidine or vise versa
indel stands for
insertion and deletion
examples of indel mutations
huntingtons and fragile x syndrome
forward mutations
alter the function of a gene
back mutations are also known as
revertants
back mutations
reverse the effect of forward mutations
why can insertions be reversed but deletions cannot?
insertions can be removed, deletions are gone forever.
mutation hotspot
a spot in the genome where mutation frequency is increased by at least an order of magnitude
many mutational hotspots result from
the presence of modified bases
a common modified base is
5-methylcytosine
where is 5-methylcytosine found
compacted chromatin
example barr body
5-methylcytosine can be deaminated into
thymine
cytosine can be deaminated into
uracil
silent mutation
a neutral substitution
causes change in sequence but does not affect activity
null mutation
eliminates function of a gene
dominant negative
does not have a function but suppresses functioning genes
a locus with multiple functional alleles is considered
polymorphic
codons
triplicate combinations of nucleotides
genetic code
the relationship between a DNA sequence and the sequence of the polypeptide
reading frame
ways a nucleotide sequence can be translated into a polypeptide
in DNA, how many reading frames are possible
6
in mRNA, how many reading frames are possible
3
open reading frame
a sequence of DNA consisting of triplicates that can be translated into amino acids starting with an initiation codon and ending with a termination codon.
gene expression
the process by which information contained within a sequence of DNA is used to produce an RNA or polypeptide
basic gene expression
DNA to mRNA to polypeptide
template strand
antisense strand
minus strand
3’-5’
nontemplate strand
sense strand
coding strand
5’-3’
mRNA structure
5’UTR
coding region
3’UTR
a gene is usually … than the sequence encoding the polypeptide
longer
how is mRNA processed in eukaryoyes
5’ cap
polyAtail
removal of introns
exon
any segment of an interrupted gene that is represented in the mature RNA
introns are removed from the pre-mRNA via
splicing
translation is facilitated by the
ribosome
ribosome
a large assembly of RNA and proteins that synthesizes polypeptides under direction of a mRNA template
ribosomal RNA
major structural component of ribosomes
transfer RNA
attaches amino acids in order of the mRNA
regulatory genes are
trans acting
