IMMS Flashcards
What is a Karyotype?
number and appearance of chromosomes in a cell
Each chromosome contains a DNA duplex of roughly how many base pairs?
10^7
What is the letter for the short arm of the chromosome?
p
What is the letter for the long arm of the chromosome?
q
What are the long and short arms of a chromosome separated by?
centromere
How many genes are there roughly in humans?
22,000
What does mitosis produce and what is the purpose of it?
produces 2 daughter cells that are genetically identical to parent cells. Growth and replace dead cells
What is the term given to cells: not in replication, during replication and after replication?
chromatin, chromosomes, chromatids
What 4 things occur in G1 stage of interphase?
rapid growth
normal metabolic function
new organelles produced
protein synthesis of proteins involved in spindle formation
What 3 things happen during synthesis stage of interphase?
DNA doubles through DNA replication
Histone proteins double through protein synthesis
Centrosome replication
What 3 things happen during G2 stage of interphase?
Chromosomes condense
Energy stores accumulate
Mitochondria and centrioles double
What 2 things happen during Prophase?
chromatin condenses into chromosomes
centrosomes nucleate microtubules and move to opposite poles of nucleus
What 4 things happen during Prometaphase?
nuclear membrane breaks down
microtubules invade nuclear space
chromatids attach to microtubules
cell no longer has a nucleus
What happens in metaphase?
chromosomes line up along equatorial plane
What happens in anaphase?
sister chromatids separate and are pushed to opposite poles of the cells, centromere first, as spindle fibres contract
What 3 things happen during Telophase?
nuclear membrane reforms
chromosomes unfold into chromatin
cytokinesis begins
What 2 things happen during Cytokinesis?
cell organelle become evenly distributed around each nucleus
cell divides into two daughter cells with a nucleus in each
What are 5 differences of meiosis compared to mitosis?
only in gametes
recombination of genetic material results in genetic diversity
2 cell divisions
4 haploid cells produced which are genetically distinct from each other and parent cell
not a cycle
What happens in meiosis 1?
chromosome number is halved
How and when is genetic diversity created in meiosis 1?
Crossing over between non-sister chromatids in Prophase 1
Random assortment on the metaphase plate in Metaphase 1
What happens in Meiosis 2?
Sister chromatids separate
Haploid cells are produced
How are spermatogonia formed?
lots of mitoses from primordial germ cells
How many sperm per ejaculate?
100/200 million
How are oogonia produced?
30 mitoses from primordial germ cell
When do oogonia enter prophase 1 of meiosis?
8th month of intrauterine life
how does the cytoplasm divide for female gametogenesis?
unequally, forms 1 egg and 3 polar bodies that apoptose
When are meiosis 1 and 2 completed?
meiosis 1 is completed at ovulation
meiosis 2 is only completed if fertilisation occurs
What are 2 problems with meiosis?
Non disjunction
Gonadal mosaicism
What is non-disjunction?
failure of chromosome pairs to separate in meiosis 1 or sister chromatids to separate properly in meiosis 2
What is Gonadal Mosaicism?
occurs when precursor germline cells to ova or spermatozoa are a mixture of 2 or more genetically different cell lines
What are the 3 main causes of disease?
Genetic
Multifactorial
Environmental
What is the locus?
the position of a gene/DNA on the genetic map
What is polymorphism?
frequent hereditary variations at a locus
What is consanguinity?
reproductive union between 2 relatives
What is autozygosity?
homozygous by descent, inheritance of the same mutant allele through 2 branches of the same family
What is hemizygous?
gene that is carried on an unpaired chromosome
What is Penetrance?
proportion of people with a gene/genoptype who show the expected phenotype
What is lyonisation?
the process of X chromosome inactivation
What is the function of the nucleus?
houses DNA in the form of chromatin within the nucleolus
What is the function of mitochondria?
site of oxidative phosphorylation
What is the outer and inner membrane of mitochondria the site of?
outer = lipid synthesis and fatty acid metabolism inner = respiratory chain ATP production
What is the matrix and intramembranous space of the mitochondria the site of?
matrix = tricarboxylic acid (Krebs) cycle
intramembranous space = nucleotide phosphorylation
What is the structure and function of rough endoplasmic reticulum?
highly folded flattened membrane sheets
site of protein synthesis
What is the structure and function of smooth endoplasmic reticulum?
highly folded flattened membrane sheets
sit of membrane lipid synthesis, processes and stores synthesised proteins
What is the structure and function of golgi (cis medial and trans)?
parallel stacks of membrane
Cis receives smooth endoplasmic reticulum vesicles - protein phosphorylation occurs
Medial modifies products by adding sugars, forms complex oligosaccharides by adding sugars to lipids and peptides
Trans proteolysis of peptides into active forms and sprting of molecules into vesicles which bud from the surface
Function of lysosomes?
contain digestive enzymes breakdown for most molecules
Function of peroxisomes?
contain enzymes that oxidase long chain fatty acids
produce hydrogen peroxide which can be used to destroy pathogens
What is lipofuscin?
membrane bound orange-brown pigment, peroxidations of lipids in older cells, common in heart and liver
What are oligosaccharides?
3-12 monosaccharides
What are proteoglycans?
long, unbranched polysaccharides radiating from a core protein
What are the properties of peptide bonds?
very stable
cleaved by proteolytic enzymes
can have partial double bonds
flexibility around C atoms not involved in bond thus allows multiple conformations
What is the primary structure of a protein?
linear sequence of amino acids held together by covalent bonds
What is the secondary structure of a protein?
alpha helix - h bonds between each carbonyl group
beta pleated sheet - h bonds between linear regions of polypeptide chains
What is the tertiary structure of a protein?
electrostatic, hydrogen and covalent bonding
folding into a globular structure
What is the quaternary structure of a protein?
2 or more tertiary structures joined together to form a protein
What is an isoenzyme?
enzymes that have a different structure and sequence but catalyse the same reaction
What is a coenzyme?
cannot themselves catalyse a reaction but bind to an enzyme to activate it
What are activation-transfer coenzymes?
form a covalent bond and are regenerated at the end of the reaction
What are oxidation-reduction coenzymes?
electrons are transferred from one compound to the other
What is myoglobin?
found in the muscle, serves as a reserve supply of oxygen and facilitates the movement of O2 in muscles
In which direction is DNA synthesised and why?
5’to3’ as DNA polymerase reads template strand from 3’to5’
What enzymes are involved in DNA replication?
Topoisomerase DNA helicase DNA polymerase Primase enzyme RNAse H
What is the role of topoisomerase in DNA replication?
unwinds the double helix by relieving the supercoils
What is the role of DNA helicase in DNA replication?
separates the DNA apart by breaking hydrogen bonds between bases, exposing nucleotides
What is the role of the primer in DNA replication?
short strand of DNA that us the start point for DNA synthesis
What is the role of the single strand binding protein in DNA replication?
keeps 2 strands of DNA apart whilst synthesis of DNA occurs, prevents annealing to form double stranded DNA
What is the role of primase enzyme in DNA replication?
RNA polymerase that synthesises the short RNA primers needed to start the strand replication process
What is the role of RNAse H?
removes the RNA primers that previously began the DNA strand synthesis
Where is the promotor region?
5’ of the 1st exon
When mRNA leaves the nucleus what type ribosome does it attach to?
80s
What is exon shuffling and what does it allow?
exons are not in the same order allows huge variants of antibodies to be produced
What does degenerate but unambiguous mean?
many amino acids specified by more than one codon but each codon specifies only one amino acid
What 3 factors can turn off gene expression?
activation of repressors
enzymes no longer activated
transcription and processing proteins required for RNA transcription and or processing are no longer produced
What is a mis-sense mutation?
single nucleotide change results in a codon that codes for a different amino acid
What is a non-sense mutation?
mutation that produces a stop codon resulting in an incomplete usually non-functional protein
What is a splice-site mutation?
affects the accurate removal of an intron
What is expansion of a tri-nucleotide repeat and what happens in Huntingtons?
normal range of repeats in first part of coding sequence is 15-20. repeats larger than 36 of CAG patient develops Huntingtons. More repeats=earlier onset
What is Anticipation?
repeats get bigger when they are passed onto next generation resulting in earlier symptoms of greater severity
What is Homeostasis?
property of a system in which variables are regulated so that internal conditions remain stable and relatively constant
What happens in Autocrine secretion?
chemical is released from cell into the extracellular fluid and then acts upon the very cell that secreted it
What happens in Paracrine secretion?
chemical messengers involved in the communication between cells, released into extracellular fluid, travel short distances, local communication
What happens in Endocrine secretion?
production and secretion of hormones into blood, travel longer distances, systemic communication, can affect the whole body
What happens in Exocrine secretion?
secretion into ducts then into organ
What are the 3 classified types of hormones?
Peptide
Steroid
Amino-acid derivative
Explain properties of peptide hormones?
- made from short chain amino acids
- vary in size
- some have carbohydrate side chains
- large, hydrophilic charged molecules that cannot diffuse across a membrane
- bind to receptors on membranes
- fast response
Explain properties of steroid hormones?
- synthesised from cholesterol
- water insoluble and lipid soluble
- cross membranes but requires transport proteins in blood
- targets an intracellular receptor
- slow response
Explain properties of amino-acid derivative hormones?
- synthesises from tyrosine
- acts in same way to peptide hormones