DNA genes and chromosomes Flashcards
what is the difference between a chromosome and chromatid
chromatids are half of a chromosome
they contain the same genetic material
what is a homologous chromosome
chromosome pairs with the same centromere position one from mother and one from father
but they are genetically different
describe how DNA is wound into a chromosome
DNA double helix is wound around a histone and the complex then coils.
this coil is further coiled and packaged into a chromosome.
what is the haploid number
23
what is the diploid number
46
what is an allele
version of a gene
what is a phenotype
physical expression of a gene
what is a genotype
genes you contain
why do we have a triplet code
so that we have enough combinations to code for each amino acid
what is a locus
the place a particular section of DNA is located
what does the base sequence of each gene contain
amino acid sequence in a polypeptide
functional RNA , ribosomal RNA and transfer RNA
what is an intron
non coding DNA
what is an exon
coding DNA
what are the bonds between base pairs
hydrogen
what are the bonds between base pairs and backbone
phosphodiester
what are the bonds between amino acids
peptide bonds
where are triplet codes found
DNA
where are codons found
MRNA
where are anticodons found
TRNA / proteins
what does degenerate mean
amino acids have more than one triplet code
what does universal mean
the same triplet of DNA bases are for the same amino acids in all organisums
what does non overlapping mean
each DNA base in each triplet is only read once
what do genes code for
ribosomal RNA and transfer RNA
are introns and exons found in prokaryotic cells
only exons
what is transcription
production of MRNA using a DNA template. A gene is transcribed into an MRNA molecule
what is translation
the production of polypeptides using the sequence of codons carried by MRNA
occurs in a ribosome
describe transcription
DNA helicase unwinds sections of DNA ro expose the bases by breaking hydrogen bonds
RNA polymerase attaches to the exposed polynucleotide and joins complementary RNA nucleotides together forming pre MRNA
Pre MRNA is is then spliced to form MRNA which diffuses out of the nucleus
what is splicing
removing introns from pre MRNA allowing different proteins to be made
similarities of transcription and DNA synthesis
DNA helicase is used
phosphodiester bonds are made
use complementary base pairs
differences of transcription and DNA synthesis
RNA polymerase in transcription instead of DNA polymerase
Pre MRNA is formed in transcription whilst DNA synthesis produces two DNA molecules
splicing is required in transcription but not in DNA synthesis
DNA synthesis does the whole chromosome
transcription is just one gene
what does TRNA do
it had an amino acid attachment site and an anticodon loop consisting of 3 unpaired bases making TRNA specific to each amino acid
why do amino acids need ATP in TRNA
so that it is activated to be picked up by TRNA
describe translation
MRNA associates with ribosomes in the cytoplasm
the first two codons are on the ribosome and attract their complementary TRNA
anticodons of the TRNA join via complementary base pairing forming hydrogen bonds
with MRNA codons
peptide bonds are formed
ribosome moves onto the next codon
the first TRNA leaves the ribosome and a new one enters
another peptide bond is formed between the second amino acid and the new one
this continues until the ribosome reaches a stop codon
what does transferase do
creates peptide bonds between amino acids and breaks bonds from TRNA
what does a stop codon do
codes for a release factor not an amino acid
