IMMS genetics, organelles and macromolecules

Question 1

What is a karyotype? Spreads are arranged in what order?

Answer 1

Number and appearance of chromosomes in a cell.

Size order- biggest is pair 1 and smallest is pair 22.

Question 2

Each chromosome has what two arm types?

Answer 2

Long arm (q) and short arm (p)

Question 3

What happens during pro metaphase?

Answer 3

Nuclear membrane breaks down, microtubules invade nuclear space, chromatids attach to microtubules and the cell no longer has a nucleus.

Question 4

Downs syndrome is an extra chromosome what? Something is defined as malignant if there are too many what?

Answer 4

Chromosome at 21(trisomy 21)

Mitotic figure i.e. lots of nuclei of different sizes

Question 5

What happens in prophase 1 of meiosis? During metaphase 1?

Answer 5

Crossing over occurs between non-sister chromatids

Random assortment on metaphase plate

Question 6

First stage of gametogenesis? Timing of mitosis in germ cells differs greatly between what?

Answer 6

Proliferation of primordial germ cells by mitosis

Males and females

Question 7

Name of mature sperm? Type of sperm present at birth? Process of sperm production takes how long?

Answer 7

Spermatogonia
Primary spermatocytes
60-65 days

Question 8

In females, primordial germ cells undergo 30 mitoses into what? Enter prophase 1 by what month of intrauterine life? Cells enter ovulation how long later? Cytoplasm divides unequally into what?

Answer 8

Oogonia
8th month
10-50 years later
1 egg and 3 polar bodies- that apoptose

Question 9

Meiosis 1 occurs at what stage? Meiosis 2 only completed if what occurs?

Answer 9

Ovulation

Fertilisation

Question 10

What is non-disjunction? What is monosomy?

Answer 10

Failure of chromosome pairs to separate in Meiosis 1 or sister chromatids to separate properly in meiosis 2.
Loss of a chromosome- e.g. Turners syndrome- only 1 X chromosome

Question 11

What is gonadal mosaicism? Due to what? Who is healthy and who is diseased?

Answer 11

Precursor germline cells to ova or spermatozoa are mixture of two or more genetically different cell lines. Due to errors in mitosis. One line= normal, other= mutated.
Parent= healthy, foetus may be diseased.

Question 12

What gender is gonadal mosaicism more common in? What forms of inheritance?

Answer 12

Males- most commonly autosomal dominant and X-linked.

Question 13

3 causes of disease? Examples of multifactorial diseases?

Answer 13

Genetic, multifactorial and environmental.

Spina bifida, cleft palate, diabetes, schizophrenia.

Question 14

What is polymorphism? What is consanguinity? What is autozygosity?

Answer 14

Frequent hereditary variations at a locus.
Reproductive union between two relatives.
Homozygous by descent- inherit same mutant allele through two branches of same family.

Question 15

What does hemizygous mean?

Answer 15

Describes genes that are carried on an unpaired chromosome- refers to a locus on an X chromosome in a male.

Question 16

What does penetrance mean? Two types?

Answer 16

Proportion of people with a gene/ genotype who show the expected phenotype.
Complete- gene/ genes for trait expressed in all of population.
Incomplete- genetic traits only expressed in parts of a population.

Question 17

What is variable expression? What is sex limitation?

Answer 17

Variation in type and severity of a genetic disorder between individuals with same gene alteration.
Expression of certain feature limited to one of the sexes.

Question 18

If multifactorial condition is more common in one particular sex, relatives of who will be more affected?

Answer 18

Relatives of affected individual of less frequently affected sex will be a high risk than relatives of an affected individual of more frequently affected sex.

Question 19

What does late-onset mean?

Answer 19

Condition not manifested at birth but is classically adult-onset e.g. Huntington’s.

Question 20

What is an autosomal dominant disease? 3 reasons why both parents may be unaffected? Only method of what inheritance?

Answer 20

A disease that only manifests in the heterozygous state, affect males and females in equal proportions and in multiple generations.
Don’t have genes for it, gonadal mosaicism, or mother has reduced penetrance/ variable expression.
Only way to pass on disease from male to male.

Question 21

What is an autosomal recessive condition? Offspring has what % for being carrier/ affected? Healthy siblings have what % of being carriers?

Answer 21

A disease that manifests in the homozygous state.
25% of being affected, 50% of offspring being a carrier.
2/3 chance.

Question 22

Features of autosomal recessive disease?

Answer 22

Males and females affected in equal proportions, affected only in a single generation, parents can be related (consanguineous)

Question 23

When looking at probabilities to see risk of being carriers, who is disregarded?

Answer 23

The already affected child is disregarded.

Question 24

In X-linked disease, all daughters from affected male are what? What is it usually transmitted through? X-linked dominant example? X-linked recessive example?

Answer 24

Carriers.
Through unaffected females.
Alport’s syndrome
Duchenne’s muscular dystrophy.

Question 25

What is lyonisation? Why is this done?

Answer 25

Process of X chromosome inactivation- one of 2 X chromosomes in every cell in a female is randomly inactivated early in embryonic development.
Prevents female cells having twice as many gene products from X chromosome as males.

Question 26

Name of the inactive X chromosome in female cells? What is imprinting?

Answer 26

Barrbody- packaged in heterochromatin so cannot be transcripted.
Some genes only has 1 out of 2 alleles active- for certain ones, it is always paternal/ maternal allele.

Question 27

Classification of genetic disease?

Answer 27

Chromosomal, Mendelian- autosomal dominant/ recessive/ X-linked, non-traditional= mitochondrial, imprinting and mosaicism.

Question 28

What does the cis(first) Golgi receive? What happens here?

Answer 28

SER vesicles

Protein phosphorylation

Question 29

What does the medial Golgi do?

Answer 29

Modifies products- adds sugars to form complex oligosaccharides by adding sugars to lipids and peptides.

Question 30

What does the trans Golgi do? In most cells Golgi cannot be seen- why can it be seen in plasma cells?

Answer 30

Proteolysis of peptides into active forms and sorts molecules into vesicles which bud from surface.
Secretes substances i.e. antibodies.

Question 31

Types of vesicles?

What do peroxisomes contain?

Answer 31

Cell-surface derived (pinocytic and phagocytic), Golgi-derived transport vesicles, ER- derived, lysosomes and peroxisomes.
Enzymes which oxidase long-chain fatty acids- used in beta-oxidation

Question 32

What does the cytoskeleton do?

Answer 32

Brace the internal structure of cells- maintains their shape and internal organisation.

Question 33

Microfilaments are made from what and forms what? Width?

Answer 33

Actin- forms a bracing mesh on inner surface of cell membrane.
5nm

Question 34

Function and width of intermediate filaments? 6 proteins made of and each found where?

Answer 34

Spread tensile force through tissues= 10nm

1) Cytokeratins- epithelial cells
2) Desmin- myocytes
3) Glial fibrillary acidic protein- support neurones in brain
4) Neurofilament protein- neurons
5) Nucelar laminin- nuclei of all cells
6) Vimentin- mesodermal cells

Question 35

Microtubules made from what and width? Arise from where? Found where?

Answer 35

Tubulin(alpha and beta arranged in groups of 13 to form hollow tubes)= 25nm
Centrosome
In all cells- except erythrocytes

Question 36

What is lipofuscin? Common where? Found in who?

Answer 36

Membrane-bound orange-brown pigment- peroxidations of lipids in older cells
In heart and liver
In older people- sign of wear and tear

Question 37

Glucose+ galactose forms what? Glucose+ fructose forms what? 2 glucoses forms what?

Answer 37

Lactose
Sucrose
Maltose

Question 38

What does an aldose have? What does a ketone have?

Answer 38

An aldehyde (C1) 
A ketone (mostly C2)

Question 39

2 types of monosaccharide? Carbon has what characteristic? What properties do D and L have? Most sugars are what type?

Answer 39

D and L- aldehyde/ ketone reacts with hydroxyl group of same molecule to form ring structure.
Is a chiral centre
Same chemical, but different biological properties.
D form

Question 40

2 glycosidic bond types?

Answer 40

O-bonds- form disaccharides, oligosaccharides and polysaccharides
N-bonds- found in nucleotides and DNA

Question 41

Oligosaccharides contain how many monosaccharides? What are proteoglycans?

Answer 41

3-12 MS

Long, unbranched polysaccharides radiating from core protein (found in animals)

Question 42

Are most amino acids in the D or L form? At different pH, carboxyl and amino groups are what?

Answer 42

In the L form.

Ionised

Question 43

Properties of peptide bonds?

Answer 43

Very stable, cleaved by proteases, can have partial double bonds, flexibility around C atoms not involved in bond.
Usually one preferred confirmation (i.e. R1 and R2 (residual group)- same side or different side

Question 44

How many amino acids do peptides and proteins have?

Answer 44

Protein= 50+ amino acids 
Peptide= less than 50 amino acids

Question 45

2 secondary structures of a protein? Chain folding back (usually a 4 aa turn) is called what?

Answer 45

Alpha helix- H-bonds between carbonyl group H attached to N which is 4 aa along the chain.
Beta-pleated sheet- H-bonds between liner regions of PPCs. Chains from 2 proteins/ same protein.
Hairpin loop/ Beta-turn

Question 46

What are super-secondary structures? Bonding involved in tertiary structure? Globular structure formed from what bonds?

Answer 46

Often consist of combinations of alpha and beta structures e.g. leucine zipper, zinc finger
Electrostatic, H-bonds and covalent bonds.
Ionic bonds, disulphide bridges and Van Der Wall forces.