IMMS Flashcards
Introduction to Medicine and Medical Sciences
What is the difference between prokaryotes and eukaryotes
Prokaryotes have no nuclear membrane, all DNA in a single chromosome
Eukaryotes have their DNA within a nucleus. Some DNA in mitochondria
Functions of DNA
Template for Transcription and Translation
Basis of Genetic Disease
What is Mitosis
Process of cell division that creates 2 genetically identical daughter cells
What are the phases of the cell cycle?
G1
S
G2
Mitosis
What happens during G1?
Cell grows in size
What happens during G2?
Proteins that are needed for cell division are produced
What happens during S phase?
DNA replication
What are the stages of Mitosis? (5)
Prophase Prometaphase Metaphase Anaphase Telophase
What happens during Prophase?
Chromatin condenses into chromosomes
Centrosomes move to opposite poles of the cell
What happens during Prometaphase?
Nuclear membrane disintegrates
Spindle attaches to Chromatids
What happens during Metaphase?
Chromatids line up at the equator of the cell
What happens during Anaphase
Chromatids get separated and move to opposite poles of the cell
What happens during Telophase
Nuclear envelope reforms
Chromosomes unfold into Chromatin
Differences between Meiosis and Mitosis
Mitosis is in Somatic Cells, Meiosis is in Gametes
Meiosis has 2 cell divisions, Mitosis has 1
Mitosis creates 2 genetically identical daughter cells, Meiosis creates 4 genetically different daughter cells.
When does Crossing Over occur
Prophase I
How is genetic diversity produced in Meiosis
Independent Assortment
Crossing Over
What is the process of maturation for a sperm cell (3)
Primordial Germ Cells -> Mitoses -> Spermatogonia
Difference between Egg cell production and Sperm cell production
After Meiosis II for Sperm cell, 4 EQUAL gametes
After Meiosis II for Egg Cell, 1 Gamete and 3 Polar Bodies
Meiosis I occurs for egg cell pre birth of female, whereas meiosis initiates during puberty for male
What is the process of maturation for an Egg cell
Primordial Germ Cells -> 30 Mitoses -> Oogonia
What is non-disjunction
Failure of Chromosome pairs to separate during Meiosis I, or Sister Chromatids to separate during Meiosis II
What is Gonadal Mosaicism
Occurs when precursor germline cells to Spermatazoa are a mixture of two or more cell lines
i.e one cell line is mutated and one is not - some sperm will have a mutation and others won’t (or eggs)
Why does the risk of Gonadal Mosaicism increase with paternal age
Increasing time = Increasing chance of mutation
Where is DNA found
Nucleus AND MITOCHONDRIA
What are the stages of coiling in DNA?
Nucleosomes -> Supercoils -> Chromosomes
Describe the process of DNA replication (5)
TOPOISOMERASE uncoils the DNA
DNA Helicase breaks the H bonds between CBP, 2 strands are held apart SSb
DNA polymerase lines up complimentary free nucleotides along the separated strands in an antiparallel 5’ to 3’
Leading Strand 5’ -> 3’ is synthesised in a continuous fashion
Lagging strand 3’ to 5’ is synthesised in pieces called Okazaki fragments joined by DNA ligase
Differences between RNA and DNA
DNA is double stranded DNA has a deoxyribose sugar RNA is single stranded RNA has a Ribose sugar RNA has U instead of a T
By what process is mRNA made
Transcription
What is rRNA used for
4 types of rRNA combine with each other to form 80s Ribosomes
What is the function of tRNA
Carries an anti-codon complimentary to triplet codon, which is also attached to an Amino Acid
4 features of DNA
Unambiguous - one codon for one AA, one AA has more than one codon
Degenerate - 3 bases for a codon
Non overlapping - Successive triplets read in order
Universal
What is an alternative version of a gene called
Allele
What is a polymorphism
Variation in an allele from person to person
Structure of a gene
Promoter region - switches the gene on
Exons - coding regions of DNA
Introns - non coding regions
What is splicing
Removal of introns from pre-mRNA
what is alternative splicing
Splice site varies - different proteins can therefore be made
What is a splice site variant
The position along the base sequences at which splicing occurs changes
What is a Non-Sense mutation
Codon is changed to a STOP CODON
Caused by out of frame deletion
Mis-Sense mutation?
Single base substitution which changes type of AA
What is Allelic Heterogeneity?
Lots of different variations of one gene
What is Locus Heterogeneity?
Variants in different gene give the same clinical conditions
What is a mutation?
Damage to DNA sequence
What are the causes of mutation
Environmental (Radiation, Chemical, Thermal)
Spontaneous change
Ways in which a dominant mutation effects normal function? (3)
- ) Loss of Function - Changes in the amount of protein produced affect very sensitive pathways - stops working
- ) Gain of Function - Increased protein production
- ) Dominant Negative Mutations - Protein from mutant allele interferes with protein from normal allele
Causes of disease (3)
Genetic
Environmental
Multifactorial ( most common)
What is a Genomic disorder?
A condition that results from STRUCTURAL CHANGE to the genome, rather than DNA base change
What is Lyonisation?
Only 1 of 2 allele active - therefore recessive alleles can be expressed even if heterozygous
What are the categories of genetic disorder (4)
Chromosome Abnormality
Single gene
Polygene
Multifactorial
Common chromosome structural abnormalities (7)
Reciprocal - Transfer of Genetic material
Robertsonian Translocation - Joining of 2 chromosomes
Deletions - loss of part of a chromosome
Insertions - 1 section of a chromosome is inserted into another
Inversions - Segments of chromosome is reversed
Ring Chromosomes - Breaks occur in arms of chromosomes, and so chromosomes bind
Fragile site - Gap in chromosome which is likely to break
What are the 2 types of mosaicism
Gonadal
Somatic
What is somatic mosaicism
Genetic disorder confined to a part of the body, due to mutation in early development
What is penetrance
% of individuals with a specific genotype showing the expected phenotype
What is expressivity
Range of phenotypes expressed by a specific phenotype
What is anticipation
Where genetic disorders affect successive generations earlier or more severely than expected
What is the role of the nucleolus
Synthesise rRNA
What are the two types of DNA found in a cell
Euchromatin
Heterochromatin
If a cell is active it will contain what type of DNA
Euchromatin
If a cell is inactive, it will contain what type of DNA
Heterochromatin - will stain dark
