Genetic information(mutation,meiosis, proteinsyntheis) Flashcards
what is dna described as?
universal, non overlapping, degenerate
what does universal mean
each triplet codon codes for the same amino acid in all living organisms
what does non overlapping mean
each DNA triplet and gene is separate from each other
what does degenerate mean
the same amino acid can be coded for by more than one triplet
what is a genome
the complete set of genes in a cell/organism
What is a proteome
the full range of proteins that a cell can make
Describe the DNA in eukaryotes
-long, linear, double helix
-found in nucleus
-folded around proteins called histones
-folded into chromosomes
Describe the DNA in prokaryotes
-shorter and circular(loop)
-no proteins/histones
-no nucleus
-have plasmids
Describe the DNA in mitochondria and chloroplasts
same as prokaryotes
no plasmids
What is a gene
a section of DNA that codes for the sequence of amino acids in polypeptide or functional RNA
What is a locus
The location of a gene on a strand of DNA/chromosomes
What is a DNA triplet
a sequence of 3 DNA bases that codes for a specific amino acid
How can a genetic code be read?
when a protein is in demand, the DNA is unwound
What are introns?
A sequence of DNA within a gene that does not code for amino acids and is removed during RNA splicing before translation
What are exons?
A sequence of DNA within a gene that codes for amino acids and remains in the mRNA after splicing, forming the final transcript used in translation
What is mRNA?
RNA that transcribes and then carries DNA code out of the nucleus
Each RNA triplet is called?…
a codon. codons code for amino acids
Where are proteins made up in?
the cytoplasm
What is mRNA used for?
DNA is too big to exit the nucleus so mRNA transcribes DNA code and carries the information out of the nucleus.
What is mRNA used for?
DNA is too big to exit the nucleus so mRNA transcribes DNA code and carries the information out of the nucleus.
Compare the structure of DNA and RNA
DNA is double stranded whereas RNA is single stranded
DNA is longer whereas RNA is shorter
DNA contains thymine whereas RNA contains uracil
DNA contains deoxyribose whereas RNA contains ribose
what is transcription
the process of taking a single gene of DNA and copying it into a structure called RNA
ET- what happens during transcription
1-dna strands separate by breaking H-bonds
2-only template strand is used to make mRNA
3-complementary base pairing occurs
4-adjacent RNA nucleotides joined by RNA polymerase
5-pre-mRNA formed
6-splicing/introns removed to form mRNA
What is splicing?
pre-mRNA turns to mRNA
removes introns and joins exrons
what is translation
mRNA travels to a ribosome where proteinsynthesis occurs. The mRNA code is translated into an amino acid sequence. Each codon codes for an amino acid.
ET-what is the process of translation
1-ribosome attaches to mRNA
2-ribosome moves to the start codon
3-tRNA carries a specific amino acid
4-anticodon (on tRNA) is complementary codon(on mRNA)
5-ribosome moves along to next codon
6-process repeated snd amino acids join by peptide bonds, condensation reaction (to form polypeptide)
What is tRNA?
-tRNA works with the ribosome to translate mRNA
-tRNA transfers free amino acids from the cytoplasm to the ribosome to begin protein synthesis
-it acts like a ‘taxi’ service for amino acids
describe the role of tRNA in the process of translation
-tRNA brings specific amino acid
-amino acids are carried/transferred to ribosome
-tRNA anticodon complementary to codon
-allows for correct sequence of amino acids along polypeptide
What is the shape of tRNA?
clover shape
Give differences between the structure of mRNA and the structure of tRNA
-mRNA is longer/has more nucleotides than tRNA
-mRNA is a straight molecule but tRNA is clover-leaf shaped molecule;
-mRNA contains no paired bases/h-bonds but tRNA has some paired bases/h-bonds
-mRNA has no amino acid binding site but tRNA does
-many different mRNA, few (20 or 64)
tRNAs
-tRNA has anticodon, mRNA does not
what is the difference between mitosis and meiosis?
mitosis is for growth-meiosis is for making gametes
mitosis is for repair of tissues-meiosis is not
mitosis is for making identical daughter cells with no variation-meiosis is for making 4 unique gametes with genetic variation
mitosis is for making a full set of chromosomes(diploids)- meiosis is for making half a set of chromosomes(haploids)
what are diploids?
full sets of chromosomes
what are haploids?
half a set of chromosomes
what does n and 2n refer to?
n=haploid number
2n=diploid number
Where does meiosis occur?
in cells or testes/ovaries
Why does meiosis occur ?
makes 4 unique gametes with genetic variation
creates half a set of chromosome(haploids)
What happens before meiosis occurs?
interphase(DNA growth and replication)
How does the chromosome number change before and after interphase and explain this change.
46 chromosomes before interphase
46 chromosomes after interphase
why? we count the chromosomes by the number of centromeres present. there are 46 chromosomes(and 46 chromatids) before interphase and there are 46 chromosomes(and 92 chromatids) after interphase
How many divisions are there in meiosis?
2
What happens in prophase 1?
chromosomes condense, thicken and join up with their homologous pairs.
crossing over occurs
What happens in metaphase 1?
the homologous pairs move to the middle of the cell
What happens in anaphase 1?
the chromosomes are pulled away by the spindle fibres
what happens during telophase 1?
membranes form around the chromosomes, resulting in 2 newly formed nuclei. cytokinesis follows with the splitting of the cytoplasm
what happens during prophase 2?
spindle fibres start to form
what happens in metaphase 2?
chromosomes line up in the middle of the cell in a single file line(no pairs)
what happens during anaphase 2?
the chromatids are pulled away by the spindle fibres.
what happens during telophase 2?
membranes form around chromatids, nuclei reforms. 4 cells(unique gametes)have formed
cytokinesis follows to completely split cytoplasm
What are the two ways that meiosis produces genetic variation?
-independent assortment
-chiasmata/crossing over
What is ‘crossing over’?
this is when the chromosomes are lined up in homologous pairs and exchange their genetic information between each other
What is the result of ‘crossing over’?
recombination chromosomes
ET-Explain how meiosis results in cells that have the haploid number of chromosomes and show genetic information
-homologous chromosomes pair up
-crossing over occurs/chiasmata form
-this produces new combinations of alleles
-chromosomes separate
-at random (due to independent assortment)
-produces varying combination of chromosomes
-chromatids separated at meiosis 2
ET-Describe the process of crossing over and explain how it causes genetic diversity
-homologous pairs of chromosomes associate
-chiasmata form
-sections of alleles are exchanged
-producing new combinations of alleles
What is non disjunction?
failed separation of homologous pairs OR sister chromatids leading to incorrect number of chromosomes in gametes
What is a mutation?
a random change in base/nucleotide sequence of DNA
Which point in the cell cycle are mutations most likely to occur and why?
interphase
because that is where DNA replication occurs
ET-Explain how a mutation can lead to the production of a non- functional enzyme(6)
-change in base/nucleotide sequence of DNA/gene
-change in amino acid sequence/ primary structure of the enzyme
-change in hydrogen/ ionic/ disulfide bonds
-change in tertiary structure
-change in active site
-no enzyme-substrate complexes form
Give some examples of mutagenic agents
-carcinogens
-mustard gas/tar/phenols
-uv light
-x rays/ cosmic rays
-high energy radiation/ ionising radiation
-colchicine
what are the different types of mutation?
substitution, insertion, deletion
What happens during substitution?
one or more bases are swapped for another.
genetic code degenerate/ may occur in intron
What happens during insertion?
one or more bases are added.
all based after inserted base shift right(frame shift)- all subsequent codons change
What happens during deletion?
one or more bases are removed.
all based after deleted base shift left(frame shift)- all subsequent codons change
how big of an impact does substitution have?
minor impact
how big of an impact does insertion have?
big impact
how big of an impact does deletion have?
big impact
ET- explain why a mutation involving the deletion of a base may have a greater effect than one involving substitution of one base for another.(3)
-deletion causes frame shift/alters base sequence
-changes sequence of amino acids
-whereas substitution alters one codon
