Topic 4 - DNA, RNA And Proteins Synthesis Falshcards Flashcards
Meiosis
Cell division to form gametes
2 divisions, 4 daughter cells, genetically different (crossing over, independent segregation)
Mitosis
Cell division for growth and repair
1 division, 2 daughter cells, genetically identical
DNA, genes and chromosomes in EUKARYOTES
Long linear and double helix, folded in nucleus, folded into histones (proteins), folded into chromosomes, HAVE introns
DNA, genes and chromosomes PROKARYOTES
DNA is shorter and circular, no histones, no nucleus, HAVE plasmids, NO introns
DNA, genes and chromosomes mitochondria and chloroplasts
Have their own DNA, same as prokaryotes, NO plasmids
Protein synthesis - transcription and translation
Transcription (SCRIBE) - DNA to mRNA
Translation (TRANSLATING) -mRNA to amino acid/ protein/ polypeptide
Before meiosis
Early interphase - Diploid 2n (6 chromosomes, 3 homologous pairs)
Late interphase - Diploid 2x2n (6 chromosomes, 3 homologous pairs)
Meiosis stages
Prophase 1 (2x2n)- chromosomes condense, nuclear membrane breaks down Metaphase 1 (2x2n)- homologous pairs line up, spindle forms, attaches to centromere Anaphase 1 (2x2n)- homologous pairs separate, pulled to opposite poles Telophase 1 (2xn)- nuclei reform, cell divides Prophase 2 (2xn)- nuclei breaks down Metaphase 2 (2xn)- chromosomes line up in equator, spindle forms, attaches to centromere Anaphase 2 (2xn)- chromatids are separated, pulled apart to opposite poles Telophase 2 (n)- nuclei reforms, cell divides
Transcription
DNA helicase separates DNA strands breaking the hydrogen bonds and exposing bases
Free RNA nucleotides attach to the template strand through complementary base pairing
RNA polymerase joins nucleotides together to form pre-mRNA
Hydrogen bonds reform behind this
RNA polymerase reaches a ‘stop’ triplet code it detaches
Transcription in prokaryotes and eukaryotes
Prokaryotes - DNA to mRNA, no introns/ no splicing
Eukaryotes - DNA to pre mRNA to mRNA, introns/ splicing
Translation
Ribosomes binds on to the mRNA at a start codon
Codon is reattached to an anticodon by complementary base pairing
Ribosome hold tRNA in place
Amino acids are joined together with a peptide bond
tRNA
Polynucleotide, folded by hydrogen bonds, anticodon is specific to the amino acid it carries
Crossing over
Different combination of alleles
Occurs in metaphase 1, chromatids of homologous pairs cross over and swap alleles
Independent segregation
Different combination of chromosomes
Gene mutation and primary structure
DNA is degenerate, each amino acid is coded for by more than one triplet codon, changes to DNA base might not case a change to amino acid in primary structure, no change to bonding or tertiary structure
Mutations and non functional proteins
Changes to DNA triplet during replication, changes to mRNA codon, different anticodon and amino acid (changes primary structure), different bonding, changes tertiary structure
Introns
Regions within a gene that don’t code for polypeptides
Triplet code
3 bases = 1 amino acid
What does a degenerate code do
Protects against point mutations (a single nucleotide base is changes)
Transfer of information from DNA
Nucleotide base sequence determines the sequence of amino acids in proteins
Eukaryotes- DNA found in the nucleus by protein synthesis in the cytoplasm
DNA transferred into the cytoplasm by being transcribed onto a single stranded molecule (RNA)
RNA
Single nucleotide chain
Polymer made of repeating mono nucleotide subunits
A,U,G,C
mRNA and tRNA
mRNA description
Long strand, single helix Formed in nucleus during transcription Small (leaves pores in nuclear envelope Act as template for protein synthesis Carries information in the form of codons, determines the amino acid sequence
tRNA
Small, single stranded folded into a clover leaf shape
Anticodon - sequence of 3 organic bases coding for amino acids
Splicing pre-mRNA to mRNA
Pre-mRNA is produced in transcription. The spliced to form mRNA
Introns prevent the synthesis of a polypeptide
mRNA passes through nuclear pores into cytoplasm where it is attracted to the ribosomes for translation
Mutation
If a mutation occurs during gamete formation, then these may be inherited
Gene mutation
a change to base sequences of DNA during DNA replication
Calculating chromosome combinations
2^n when n = number of pairs of homologous chromosomes
2n)^2 when n = number of pairs of homologous chromosomes (when there are two different parents
gamete
haploid sex cell
Haploid
a cell with a single set of unpaired chromosomes
diploid
a cell with two complete sets of chromosomes
fertilisation
fusion of 2 haploid gametes to form a zygote
chromosome non-disjunction
when chromosomes don’t separate properly during meiosis 1 or 2
> causes uneven number of chromosomes in the gamete
homologous pairs
one chromosomes from each parent
same gene but different alleles
parts of a chromosome
> centromere - joins two chromatids
> chromatids - exact copy of the other half
substitution
swapping one base for a different base
deletion
one base is removed (causing a frame shift)
codon
triplet of bases on mRNA that codes for a specific amino acid
anticodon
triplet of bases on tRNA that is complementary to codon on mRNA
universal
genetic molecule in all living organism
non-overlapping
each DNA triplet is separate from each other
degenerate
the same amino acid can be coded for by more than one triplet
genome
the complete set of genes in a cell/ organism
proteome
the full range of proteins that a cell can make
