IMMS Flashcards
How many chromosomes are in a normal human somatic cell?
46
What separates the p and q arms in a chromosome?
the centromere
How many daughter cells are produced in mitosis?
2
Describe a cell’s position in the cell cycle if it is in G0?
It is not in the cell cycle
What replicates in the synthesis phase of the cell cycle?
DNA and the centrosome
What happens during prophase?
- Chromatin condenses into chromosomes
- Nuclear membrane starts to break down
- Centrosomes move to opposite poles of the cell and nucleate microtubules
What happens during prometaphase?
- The nuclear membrane breaks down and the chromosomes are released into the cytoplasm
- Chromatids attatch to microtubules
What happens during metaphase?
Chromosomes line up along equatorial plane of cell (metaphase plate forms)
What happens during anaphase?
Microtubules shorten and pull the identical chromatids apart towards opposite poles of the cell
What happens during telophase?
- Nuclear membrane reforms
- Chromosomes unfold into chromatin
- Cytokinesis begins
Which chromosomal disease is trisomy 21?
Down syndrome
How many daughter cells are produced in meiosis?
4
When can crossing over occur in meiosis?
prophase 1
spermatogonia are formed from the division of what type of cells?
Primordial germ cells
How many days does it take for spermatozoa to mature?
60-65
What does non-disjunction result in?
an abnormal number of chromosomes
When does germline mosaicism occur?
when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines
What is a somatic cell?
any cell apart from a reproductive cell
What is the word for programmed cell death?
apoptosis
What is a geneotype?
The genetic constitution of an individual
What is a polymorphism?
frequent hereditary variation at a locus
What does hemizygous mean?
Only one allele
What would the karyotype of a male with Down syndrome be?
47XY+21
What is an autosomal recessive disease?
Disease that manifests in the homozygous state
What are macromolecules and give examples ?
Large biologically important molecules inside cells
e.g glycogen, haemoglobin, DNA, Collagen, Rhodopsin
Which monosaccharides form maltose?
glucose+glucose
Which monosaccharides form lactose?
glucose+glalactose
How many monosaccharides form an oligosaccharide?
3-12
What type of bond links nucleotides
phosphodiester bond
What type of bond links amino acids to form proteins?
peptide bond
Name two purines
Adenine, guanine
Name three pyrimidines
uracil, cytosine, thymine
What is the primary structure of a protein?
The sequence of amino acids
What is the secondary structure of a protein?
Defined by local conformations induced by hydrogen bonding along the peptide backbone
What is the tertiary structure of a protein?
3D arrangement of a protein molecule
What is the quaternary structure of a protein?
Structural relationship of more than one polypeptide joining together
What are the two types of coenzymes ?
Activation and oxidation
what is a porphyrin ring that contains iron called?
heme
Give two types of secondary structure
alpha helix, beta sheet
Describe the alpha helix secondary protein structure
hydrogen bonds between each carbonyl group and the hydrogen attached to the nitrogen which is 4 amino acids along the chain
Which amino acid can break the alpha helix ?
proline
How is the beta sheet formed?
Hydrogen bonds between linear regions of polypeptide chains
What is a supersecondary protein structure?
A combination of secondary structures
What are isoenzymes?
enzymes that have different structures and sequences but catalyse the same reaction
What is aneuploidy ?
Having an abnormal number of chromosomes
What is an allele?
One or more alternative forms of a gene at a given locus
What does it mean to be heterozygous?
presence of two different alleles at a given locus
What is allelic heterogeneity?
The situation where different mutations within the same gene result in the same clinical condition e.g cystic fibrosis
Give an example of an autosomal recessive disorder
cystic fibrosis
What is consanguinity?
Reproductive union between two relatives
What are the typical features of autosomal dominant inheritance?
- Males and females affected in equal proportions
- affected individuals in multiple generations
- Transmission by individuals of both sexes to both sexes
What is penetrance?
the percentage of individuals with a specific genotype showing the expected phenotype
What is expressivity?
The range of phenotypes expressed by a specific genotype
What is anticipattion?
Where a genetic disorder affects successive generations earlier or more severely
What is somatic mosaicism?
genetic mutation only present in some tissues in the body
What is gonadal mosaicism
genetic mutation only present in gonadal tissue
What is a sex-limited condition?
condition inherited in an autosomal dominany pattern that affects one sex more than another
What are the typical features of an X-linked condition?
- Usually only males affected
- Usually transmitted through unaffected females
- no male-to-male transmission
What us lyonization?
generally only one of two X chromosomes is active in each female cell
What is genomic imprinting?
an epigenetic phenomenon that causes genes to be expressed in a parent of origin specific manor
What is homoplasmy?
Describes a cell whose copies of mtDNA are all identical
What is heteroplasmy?
Variation of mtDNA within a cell
What is a codon?
Three nucleotides that code for an amino acid
What is a multifactorial condition?
Due to a combination of genetic and environmental factors
What is hereditability?
The proportion of aetiology that can be ascribed to genetic factors as opposed to environmental factorsW
What can we call the factors that influence the development of a multifactorial disorder
liability
Describe the distribution of liabilities of all individuals
normal distribution
Describe the curve of the liability/theshold model for relatives compared to the general population
Curve for relatives is shifted right
What is prevalence?
total number of people in the population who have a disease
What is incidence?
the number of new cases per year within the population that don’t yet have the disease
What is the concordance rate in the context of a twin study?
the % of twin pairs studied that both have the condition
What is the function of cholesterol in cell membranes ?
provides stability
What is the phospholipid bilayer freely permeable to?
water,gases and small uncharged polar molecules e.g urea, ethanol
What is the phospholipid bilayer impermeable to?
ions, charged polar molecules, large uncharged polar molecules
What is the function of the golgi body?
mediates protein sorting to specific sites
How many subunits to g proteins that associate with GPCRs have ?
3- alpha,beta and gamma
What is the function of adenyl cyclase?
catalyses synthesis of cAMP from ATP
Which second messengers does phospholipase C catalyse the synthesis of?
IP3 and DAG
What is paracellular transport?
transfer of substances across an epithelium by passing through intercellular space between cells
Which g protein subunit determines the type of second messenger synthesised?
alpha
What does the trophoblast develop into?
the placenta
What does the inner cell mass develop into?
the baby
What does the bilaminar disc consist of?
ectoderm and endoderm
Which layer forms between the ectoderm and endoderm?
the mesoderm
What does the ectoderm develop into?
epidermis of skin, hair and nails mammary, sweat and sebaceous glands CNS peripheral nervous system pituitary gland enamel of teeth lens of eye parts of the inner ear sensory epithelium of nose, ear and eye
what does the endoderm develop into?
epithelial lining of the GI tract, respiratory tract and urinary bladder
parenchyma of thyroid gland, parathyroid gland, liver and pancreas
epithelial lining of the tymapnic cavity and autitory tube
plays a part in the development of the notochord
what does the mesoderm develop into?
All of the musculoskeletal system deep layers of the skin abdominal and chest walls and lining the walls of the bowel (but not the lining) the urogenital system
What are the chemical messengers made by the notochord called?
sonic hedgehog
What are the somites formed from?
mesoderm
Give three types of mesoderm
Paraxial (somites)
intermediate mesoderm
lateral mesoderm
What does the paraxial mesoderm form?
The myotome
The sclerotome
The dermatome
What does the intermediate mesoderm form?
The urogenital system
What does the lateral mesoderm form?
Outer layer- covers the inside of the chest and abdominal walls- somatic layer mesoderm
Inner layer- covers the organs in the thorax and abdomen- the splanchnic mesoderm
How many hydrogen bonds are between G and C?
3
List the core histones
H2A, H2B, H3, H4
How long does the mitosis part of the cell cycle last?
1 hour
What is the longest phase of the cell cycle?
G1
What is the function of topoisomerase?
unwinds supercoiling
What is the strand that is synthesised continuously referred to as?
the leading strand
What is meant by semi-conservative replication?
The two resuling DNA copies each have one strand of parental DNA and one newly constructed strand
What is the function of helicase?
Unwinds the DNA double helix
What is the function of SSBs?
coat the single stranded DNA and prevents the strands from re-annealing
What is the function of primase?
Synthesies RNA primers
What is the function of DNA polymerase?
Joins nucelotides to form a DNA strand
What is the sliding clamp?
An accessory protein that helps to hold DNA polymerase onto the DNA strand
Which enzyme removes RNA primers from the DNA?
RNase H
Which enzyme links together short sections of DNA to make one long strand?
Ligase
In which direction does DNA synthesis occur?
5’ to 3’
What is the name of the DNA pieces separated by RNA primers in the lagging strand called?
okazaki frgaments
