What is the phenotype?
Physical manifestation of genes.
What is the genotype?
Full genetics of genes.
What is DNA composed from?
Nucleotide monomers.
What is a nucleotide composed from?
Nitrogenous base
Phosphate group
Sugar
What does the double helix shape result in?
Major and minor grooves.
Why are major grooves in the double helix important?
Binding sites for proteins.
What are the complementary base pairs of DNA?
Cytosine and Guanine
Thymine and adenine
What does uracil pair with in mRNA?
Adenine.
What is the sugar-phosphate backbone of DNA composed of?
Deoxyribose sugar and phosphate group link at 3’-5’ ends.
What does the nucleus contain?
Genetic information.
What occurs in the nucleus?
DNA replication
First steps of transcription
What is chromatin?
Chromatin is the name given to the mixture of DNA, proteins and RNA that package DNA within the nucleus.
What are heterochromatin and and euchromatin?
The condensed and extended forms of chromatin in the nucleus.
What processes require the 2 strands of DNA to separate temporarily to allow enzymes access to the DNA template?
DNA replication
Transcription
What poses a barrier to enzymes during DNA replication/transcription?
Nucleosomes and folding of chromatin barriers.
How can chromatin be made more accessible?
Histones are enzymatically modified
Histones are displaced by chromatin remodelling complexes
What is DNA replication semi-conservative?
One half of DNA is new and one is old.
In what direction is DNA replicated?
5’ to 3’.
What enzyme adds nucleotides in DNA replication?
DNA polymerase.
Why is DNA replicated in a 5’-3’ direction?
DNA polymerase can only add it in that direction.
When are chromosomes most compacted and visible?
Metaphase.
What are coding regions called?
Exons.
What are non-coding regions called?
Introns.
How does genetic code allow DNA sequences to code for proteins?
Sets of 3 form codons which code for amino acids?
What codes for the amino acid?
Codon.
What is degeneracy/redundancy of genetic code?
The fact that most proteins are coded for by more than one codon.
What is the role of RNA?
To transport DNA from nucleus to cytoplasm for ribosome travel for protein synthesis.
What is mRNA transcribed from?
DNA.
What happens during alternative DNA splicing?
Exon coding regions are reconnected in a different way to increase variation and allow generation of more protein functions.
What is the role of tRNA?
To translate the mRNA sequence into an amino acid sequence.
What does tRNA act as?
Adaptor molecule.
What is rRNA?
Component of ribosomes
Where does rRNA combine with proteins to form a ribosome?
Cytoplasm.
What is it called when several ribosomes can translate DNA at one time?
Polysome.
What are telomeres?
5’-3’ repeats.
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in prophase?
Chromosomes condense.
What happens in metaphase?
Chromosomes line up at the equator of the cell.
What happens in anaphase?
Spindle fibres form, move to opposite ends of the cell.
What happens in telophase?
New nuclear membranes form.
What is cytokinesis?
Division to form 2 daughter cells.
At what stage are chromosomes most condensed?
Metaphase.
What does mitosis produce?
Diploid cells with 46 chromosomes.
What are centromeres?
Constricted region joining sister chromatids.
When does DNA replication occur?
Interphase- S phase.
What enzymes does DNA replication require?
Helicase
DNA polymerase
Ligase
Primase
Where does DNA replication occur?
Nucleus.
What does helicase do?
Unwinds DNA from origin point by breaking hydrogen bonds.
What does primase do?
Makes RNA primers on both strands which shows DNA polymerase where to start.
What direction does DNA polymerase add in?
5’-3’.
Why does DNA polymerase add in the 5’-3’ direction?
Moves along old template in 3’-5’ direction.
What is the lagging strand?
The new strand.
What are primer fragments called and joined by?
Okazaki fragments sealed by ligase.
Why is DNA replication semi-conservative?
Because 2 copies of each contains 2 strands and one is old with the other being new.
What structure does heterochromatin have?
Condensed structure, silenced genes.
What structure does euchromatin have?
Open structure, active genes.
Are genes silenced or active in heterochromatin?
Silenced.
Are genes silenced or active in euchromatin?
Active.
What is DNA packaged with to form chromatin?
Histone proteins.
What charge do histone proteins have?
Positive.
What are DNA/chromatin/histone complexes packaged into?
Nucleosomes.
What is the karyotype?
Chromosome structure arrangement.
What happens in transcription?
RNA polymerase binds to DNA promoter region and creates template strand- it uses this to synthesis mRNA from 5’-3’ end through elongation.
What is elongation?
Synthesis of mRNA from 5’-3’ end.
What direction does RNA polymerase synthesis mRNA?
5’-3’ end.
What are the differences between RNA and DNA?
RNA is single stranded
Ribose sugar instead of deoxyribose
Uracil base instead of thymine
What happens when mRNA is produced?
Moves to ribosome for translation.
What does mRNA act as?
Specific code for proteins.
How does mRNA act as a code?
3-base codons pair with anti-codons on tRNA which are linked to amino acids.
What does tRNA do?
Links mRNA to amino acids.
What is rRNA?
Ribosomal RNA.
What are FISH probes?
Fluorescent in situ hybridisation probes.
What are the types of FISH probe?
Centromeric (number)
Telomeric (kids with mental retardation)
Whole chromosome
What are centromeric FISH probes used for?
Determining chromosome number.
What are telomeric FISH probes used for?
Subtelomeric arrangement- kids with unexplained mental retardation.
What are whole chromosome FISH probes used for?
Translocation and rearrangement.
What is meiosis?
Cell division in germline cells.
What does meiosis produce?
Haploid cells from diploid cells.
How is genetic diversity promoted within meiosis?
Recombination.
When does recombination occur in meiosis?
Prophase I
What is oogenesis?
Process of egg formation.
What is spermatogenesis?
Process of sperm formation.
Why is there more chance of mutation in sperm?
Increase division.
Where do mitochondrial genes come from?
Maternal origin.
What is X-inactivation?
Due to double XX genotype in mother, one X chromosome may be deactivated and just the other passed on.
