Midterm Flashcards
G1 phase
Growth and cellular metabolism
S phase (synthesis)
DNA replication, chromosomes duplication
G2 phase
Prepare for mitosis
M phase
Mitosis
Interphase
Time between successive mitosis’s (G1+G2+S)
G0 phase
Terminal event. eg. neutrons with axons and dendrites
Why does mitosis happen
Growth, cell replacement, healing, reproduction
Prophase
Chromosomes condense, centrosomes produce microtubules and migrate to opposite poles
Pro metaphase
Microtubules attach to chromosomes and nuclear envelope begins to break down
Metaphase
Chromosomes align in centre of cell
Anaphase
Sister chromatids migrate to opposite poles
Telophase
Nuclear envelope begins to reform, chromosomes condense
meiosis I
Randomly separates chromosomes
meiosis II
Separates sister chromatids like mitosis
M cyclin
CDK helps prepare the cell for mitosis
S cyclin
CDK helps initiate DNA synthesis
G1/ S cyclin complex
Prepares the cell for DNA replication
DNA replication checkpint
Checks for any un-replicated DNA at the end of g2 phase (before cell enters mitosis)
Cell cycle check points
Cell replication pauses to make sure it is okay for the cell to go on to the next stage. There are specialized CDK complexes to do so
DNA damage checkpoint
Checks for damaged DNA before the cell enters S phase, makes sure genes that inhibit the cell cycle are turned off
Spindle assembly checkpoint
Checks that all chromosomes are attached to spindle fibres, after DNA replication checkpoint
Oncogene
Cancer causing gene
Proto- oncogene
Normal genes important for promoting cell division, but have the potential to become cancerous if mutated
Tumour suppressors
genes that encode proteins whose normal activity inhibits cell division
Cancer development
Normal cells: Inactivation of the first tumour suppressor gene
benign cancer: Activation of the oncogene
Malignant/ metastatic cancer : Inactivation of the second and third tumour suppressor gene
Principle of dominance
In a heterozygote, one allele may conceal the presence of another
Principle of segregation
In a heterozygote, two alleles R and r separate themselves in the form of gametes
Principle of independent assortment
Alleles on different parts of chromosomes assort independently from one another (in anaphase I)
Addition
OR
Multiplicative
AND
Monogenic trait
When one gene is responsible for one trait
Polygenic trait
There are multiple genes responsible for a person’s height
Prophase I
Synapse (gene-for-gene pairing)
Bivalent (crossing over)
Chromosomes condense and nuclear envelope begins to break down
Prometaphase I
Spindles attach to kinetochores on chromosomes
Metaphase I
Mono orientation
Anaphase I
Homologous chromosomes separate but sister chromatids do not
Telophase and cytokinesis (meiosis I)
Cells go from diploid to haploid
Prophase II
Nuclear envelope breaks down and chromosomes condense
Pro metaphase II
Spindles attach to the kinetochores on chromosomes
Metaphase II
Chromosomes align in the centre of the cell
Anaphase II
Sister chromatids separate, replication in policy has already happened
Telophase and cytokinesis (meiosis II)
Cytoplasm does not divide equally
Males: Each n cell is a sperm cell
Females: 3 polar bodies and 1 oocyte (egg)
Pedigree of autosomal dominant traits
Equal in males and females
Does not skip generations
Affected offspring will have an affected parent (unless they posses a new mutation)
Pedigree characteristics of autosomal recessive traits
Equal in both sexes
Skips generations
Affected can be born to unaffected children
Appears more frequently among children of consanguineous marriages
Human sex chromosomes
There is a small region of homology where pairing occurs
Y chromosome is our smallest chromosomes
They are not similar enough for any crossing over to happen
Y linkes traits
Only boys, passed form father to sons and does not skip generations
Nondisjunction
Results in eggs with either two X chromosomes or no X chromosomes
Rare XO males receive their X chromosomes from their fathers
DNA
Polymer: deoxyribose sugar
Phosphate group: 5’ carbon (adds negative charge)
Nitrogenous base: 1’ carbon
OH group: 3’ carbon
Nitrogenous bases
Purines (double ring): Adenine and guanine
Pyridines (single ring): Cytosine and thymine
Pairing: AT (20%) and GC (30%) each
Hydrophobic
Connected by phosphidiester bonds
First level of condensation
Wrapped around histone proteins
Second level of condensation
Supercoiling due to nucleosomal interactions
Telomere
Protect the ends of chromosomes
Prevent the ends of chromosomes from fusing together
Facilitate replication of the ends of linear DNA
Central dogma
Information flows from DNA to RNA to proteins
Transcription
When RNA polymerase reads the strands of DNA and makes a new one
Centromeres
Hold chromosomes together. Satellite sequence (non- coding DNA)
Nucleotide
Group of 3 (one codon)
Third level
Attachment to non- histone protein scaffold
quaternary structure
Two or more polypeptide chains may form a double helix
RNA
Ribose sugar (OH on 2’ rather than H)
Uracil replaces thymine, this makes RNA more reactive than DNA
RNA synthesis
RNA is synthesized on mRNA molecules, from DNA
1) Initiation of RNA synthesis does not require a primer
2) New nucleotides are added to the 3’ end of the RNA molecule
3) DNA unwinds at the front of the transcription bubble and rewinds
Prokaryotic transcription
Can occur simultaneously by ribosomes
RNA splicing
Removes introns
TATA box
Promoter sequence
Post transcriptional modification
Addition of the 5’ cap: Helps ribosomes bind to 5’ end of mRNA
3’ cleavage and addition of poly(a)tail: Increases stability of mRNA, facilitates binding of ribosome to mRNA
RNA splicing
How is genetic code read
No spaces between codons and they do not overlap
Most amino acids are specified by more than one codon
Nearly universal
Reading frame defined by an AUG codon near the 5’ end of the RNA
Mutations
Can arise spontaneously as a result of an error during DNA synthesis or as a result of spontaneous chemical changes that alter the nucleotides
Co- dominance
The phenotype is between two homozygotes
Incomplete dominance
There is phenotype that is a mix of two alleles
Lethal allele
Causes death at an early stage of development, so some genotypes may not appear in the progeny. Heterozygotes are viable. Affects the mendelian genotypic/ phenotypic ratios among live births
Penetrance
The chance of an individual having a particular genotype that expresses a particular phenotype
Incomplete penetrance
When the phenotype does not relate to the genotype
Lethal allele
Causes death at an early stage of development, not common since no homozygous individuals live long enough to reproduce
Expressivity
The degree to which an allele is expressed
Polymorphism
An allele found in at least 1% of the population, the rest are mutant alleles
Wobble base pairing
When thymine and guanine pair together
Depurination
When A purine site does not provide template for T, so pairs with another A
Deamination
Removing NH2
Cytosine= uracil
5-methyl cytosine= thymine
Somatic mutations
Not passed on
Germ line mutations
Passed non
Missense
thq one big fly had one red eye
Nonsense
the one big
Strand slippage
New strand slips out… addition
Template strand slips out…. deletion
Unequal crossing over
One chromosome has an insertion, one has a deletion
Types of chemical mutation
1) Only replicating DNA
2) Both replicating and non replicating DNA
Mutations that interfere with non- coding regions
Interfere with promoter function to prevent or reduce transcription
Recessive gene mutations
Almost always involve loss of gene function
Complete loss of function
Nut allele
Partial loss of function
Hypermorphic allele
Discontinuous characteristics
Relatively few phenotypes
Continuous characteristics
qualitative EG. hair/ skin
Polygenic characteristics
Genes influenced by genes on many loci
Multifunctional characteristics
Polygenic characteristics influenced by environmental factors
Blood
O can donate to anybody
AB can accept from anybody
I^a and I^b are co dominant over I
Radiation
Chromosome breaks
Transposable elements
Inserted into staggered cuts in the DNA, different mutations can cause the same disorder
Base analogues
Molecules that have a very similar structure to a nitrogenous base
5- broumacil may be inlace of thymine, if it pairs with guanine this is bad. If it pairs with adenine it is fine
Cleft lip/ cleft plate
Ultrasound
Amniocentesis
Amniotic fluid, cells are cultured, DNA analysis and chromosomal analysis are done
Chronic villus
Catheter is inserted through vagina into contact with the chorion (outer layer of the placenta). Suction removes a piece to be used for genetic tests (no need to be cultured)
Fetal cell sorting
Fetal cells can be sorted from maternal cells
Pre- implantation genetic diagnosis
Abnormal, combined with in vitro fertilization treatments. Sampling of cells at 8 or 16 cell stage
Cystic fibrosis
Amniocentesis or Chronic villus sampling
Dwarfism
ultrasound, X rays, Amniocentesis or Chronic villus sampling
Hemophilia
Fetal blood sampling, amniocentesis or Chronic villus sampling
Lesch-nyhan syndrom
amniocentesis or Chronic villus sampling
Neural tube defects
amniocentesis, ultrasound or maternal blood tests
Osteogenesis imperfecta
Ultrasound or X rays
Phenylketonuria
amniocentesis or Chronic villus sampling
Sickle- cell anemia
amniocentesis or Chronic villus sampling
Tay- Sachs disease
amniocentesis or Chronic villus sampling
Dominant mutations
Can involve a loss or gain of gene function
Loss of function mutation
For those genes where one functional copy is not enough (also called haploinsufficiency)
Dominant negative mutation
A loss of function mutation that interferes with the wild type allele