B1 Gene Expression and Proteins Flashcards
What is the structure of DNA?
Double helix 4 bases (adenine, thymine, guanine cytosine) Phosphate- (pentose)Sugar backbone Bases form ‘rungs’ of ladder
What is the central dogma of molecular biology?
DNA –> mRNA –> Protein
What are the purine bases found in nucleic acids?
Guanine and adenine
What are the pyrimidine bases in nucleic acids?
cytosine, thymine, uracil
What is chromatin structure?
DNA wrapped around histones (basic unit of chromatin = nucleosome)
What is a nucleosome?
The basic unit of chromatin
What does the nucleosome look like?
Beads on a string
What is the difference between euchromatin and heterochromatin?
Euchromatin - ‘unpacked’ beads on a stringHeterochromatin ‘packed’
When the chromatin fibre is supercoiled and associates with non-histone proteins, what is the structure called?
Chromosomal scaffold
What are the two copies of each chromosome called?
homologues
What is the centromere?
point of attachment to the mitotic spindleWhere chromatids are attached to each other in the chromosome.
What is a chromatid?
One copy of the duplicated chromosome
What is the telomere?
The endsof the chromosome.
What is the purpose of the telomeres?
To protect the chromosome during replication
What is a karyotype?
The stereotypic number and shape of chromosomes in a species during metaphase
What is the importance of the karyotype?
Analysis can be used to diagnose gross chromosomal abnormalities
What happens during G0 phase?
Rest; the cell has not started to divide
What happens during the G1 phase?
Cell starts making more proteins and growing larger
What happens during the S phase?
DNA synthesis - chromosomes copied
What happens during the G2 phase?
The cell checks the DNA and prepares for mitosis
How long does mitosis last in the average body cell?
30 - 60 minutes
How long does the G0 phase last?
Variable; once the signal to reproduce has been sent to the cell it moves into G1.
How long does the G1 phase last?
18- 30 hours
How long does the G2 phase last?
2-10 hours
How long does the S phase last?
18-20 hours
What is the order of the stages of mitosis?
ProphasePrometaphaseMetaphaseAnaphaseTelophaseCytokinesis
What happens during prophase?
Chromosomes condenseCentrosomes migrateto opposite polesMitotic spindle starts forming
What happens during prometaphase?
Nuclear envelope breaks downSpindle microtubules attach to chromosomesSpindle microtubules start pulling chromosomes
What happens during metaphase?
Chromosomes are pulled to the equator of the cellChromosomes line up on the metaphase plate
What happens during telophase?
Chromosomes reach opposite poles and decondenseVirtually opposite of prophase
How do the spindle microtubules attach to the chromosomes?
Via the kinetochore
How are the spindle poles formed?
Through the separation of the centrosomes
What is the kinetochore?
Complex structure made of proteins that binds to specific centromeric DNA sequences.
How can the mitotic spindle form around the chromosomes?
Centrosomes move away from each other, around nuclear envelopeSpindle forms with movement of centrosomes away from each otherNuclear envelope needs to disappear (break down)
What happens during anaphase?
Sister chromatids separate and move to opposite polesWhere the chromosomes are actually pulled apart
