November mock prep- topic 4 Flashcards
gene
section of DNA that codes for a specific sequence of amino acids, making a polypeptide
locus
specific location of a gene on a chromosome
what are the 3 characteristics of the genetic code?
universal-
same for multiple organisms
non-overlapping-
each base sequence only read once
degenerate-
amino acids coded for by multiple triplets
what is the same at the start of every DNA sequence?
the start codon
what marks the end of the DNA sequence?
the stop codon
what are introns?
non-coding sequences found in a gene
what are exons?
coding sequences within a gene
when are chromosomes visible?
when a cell is dividing
what are chromatids?
one of the two strands that make up a chromosome joined at the centromere
how are chromosomes formed?
DNA combines with histone forming a DNA-histone complex
coils then folds to form loops
loops coil and pack together to form the chromosome
what is a homologous pair?
one chromosome from maternal chromosomes and one chromosome from paternal chromosomes
what is an allele?
alternative form of a gene
what happens when the base sequence of a gene changes?
a new allele is produced due to the mutation
this codes for a different amino acid creating a different polypeptide
this therefore creates a different protein
what is a codon?
sequence of 3 bases on mRNA
what is the genome?
complete set of genes in a cell
what is the proteome?
full range of proteins produced by the genome
what is the structure of RNA?
ribose sugar
phosphate group
bases- A-U/ C-G
mRNA
single helix
long strand
transcription
leaves through nuclear pores
acts as template for protein synthesis
information in form of codon
tRNA
small
around 80 nucleotides
anticodon on opposite end- specific to the amino acid
clover leaf shape with one end extended past the other where the amino acid attaches
describe transcription
process of making pre-mRNA
DNA helicase breaks hydrogen bonds exposing the nucleotides in that area, creating a template strand
bases on template strand pair with complementary RNA nucleotides using RNA polymerase
RNA polymerase reaches stop codon and detaches
describe splicing
process of making mRNA
introns removed as they are non coding and would prevent protein synthesis
functional exons are joined
describe translation
1) mRNA leaves through nuclear pore into cytoplasm
2) ribosome attaches to start codon
3) tRNA with complementary anticodon pairs up with codon, carrying a specific amino acid
4) tRNA binds with next codon carrying a different amino acid
5) ribosome moves along mRNA bringing two tRNA molecules each time with amino acids being joined by peptide bonds
6) first tRNA is released when ribosome moves to third codon so it can collect another amino acid
7) process continues until stop codon is reached
what is a mutation?
any change to the quantity or base sequence of the DNA