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IMMS > 1- Cells and Contents > Flashcards

1- Cells and Contents Flashcards

1
Q

What is the definition of the Karyotype?

A

Number and appearance of chromosomes in a cell. Arranged in size order, largest is pair 1 with the smallest pair 22.

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2
Q

What is the purpose of mitosis

A

Replace dead cells, growth and to produce two genetically identical daughter cells.
Repair

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3
Q

What stage of the cell cycle are cells that are not diving found in?

A

G0 phase

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4
Q

What occurs in the G1 growth phase of the cell cycle?

A

Rapid growth
Organelle production
Protein synthesis: including spindle formation
Normal metabolic function

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5
Q

What occurs in the synthesis stage of the cell cycle?

A

DNA replication
Centromere replication
Histone proteins double- 2x DNA at the end of the S phase.

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6
Q

What occurs during the G2 growth phase of the cell cycle?

A 
Chromosomes condense (coil up and become visible).
Energy stores accumulate
Mitochondria and centrioles double

Checks for mutations that are a risk in S phase

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7
Q

What are the stages of mitosis ?

A 
Interphase 
Prophase 
Prometaphase 
Metaphase 
Anaphase 
Telophase
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8
Q

What occurs during interphase?

A

DNA and centrosome replication occurs, producing identical sister chromatids.
Lasts between 16 and 24 hrs

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9
Q

What occurs during prophase?

A

Chromatin condenses into chromosomes and mitosis spindle is formed.

Centrioles (centrioles) move to opposite poles of the nucleus.

Nuclear membrane begins to break down

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10
Q

What occurs during premetaphase

A

Nuclear membrane completely breaks down, releasing chromosomes into the cytoplasm (no nucleus present).

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11
Q

What occurs during metaphase?

A

Chromosomes line up along the equatorial plate (metaphase plate) of the cell.

Spindles attach to centromeres

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12
Q

What occurs during anaphase?

A

Centromerers split separating sister chromatids- they are pulled to opposite poles of the cell as the spindle fibres contract towards nuclear poles.

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13
Q

What occurs during telophase?

A

Cytokinesis

Chromosomes unfold into chromatin
Nuclear membrane forms
Organelles become evenly distributed around each nucleus
Cell divides producing two genetically identical daughter cells (2N)
46 chromosomes in each.

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14
Q

How would a nucleus appear on a histological slide if the cell was undergoing mitosis?

A

Dark- the chromatids have condensed into chromosomes

Nuclei would not be the same size

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15
Q

What is an indication that a tumour is malignant and not benign?

A

Increase in the number of mitotic divisions

Number of mitotic figures is used to determine severity of the cancer: more there is, the worse is it.

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16
Q

What are the key differences between mitosis and meiosis?

A

Only occurs in gametes
Two divisions
Produces 4 haploid daughter cells
Recombination of genetic material produces diversity
Produces 4 genetically different daughter cells
It is NOT cycle process: there is a start and finish

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17
Q

What are the stages of meiosis?

A

Meiosis 1
Meiosis II

Each can be seen to have a prophase, metaphase, anaphase and telophase

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18
Q

What occurs during meiosis I?

A

Prophase 1- crossing over occurs
Metaphase 1- random assortment occurs as chromosomes align at the equatorial plate
After this initial meiosis I division two daughter cells are produced with 2N number of chromosomes

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19
Q

What occurs during meiosis II?

A

Cells divide again producing 4 haploid daughter cells

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20
Q

What is gametogenesis?

A

Process in which preecursor cells undergo divisions and differentiate to form haploid gametes

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21
Q

In oogenesis when do oogonia enter prophase of meiosis I?

A

Eggs begin as premordia cells before undergoing 20-30 mitotic divisions too form oogonia

Following the formation of oogonia they enter prophase of meiosis I by the 8th month of intrauterine life

The meiosis process is then suspended

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22
Q

In oogenesis when is meiosis I completed and when does meiosis II commence?

A

Meiosis I is completed at ovulation forming a secondary oocyte (this receives most of the cytoplasm making it a big cell)

The other small cell is termed a polar body

Meiosis II is completed at fertilisation: this forms 3 polar bodies and one egg

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23
Q

During spermatogenesis when do meiotic divisions commence?

A

Primordial cells undergo around 30 mitotic divisions forming spermatogonia

Meiotic divisions do not commence until puberty

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24
Q

What are the stages of spermatogenesis?

A

Primary spermatocytes enter meiosis 1 emerging as haploid secondary spermatocytes

These undergo second meiotic divisions to form spermatids which develop into mature spermatozoa

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25
Q

Definition of non disjunction

A

Failure of chromosome pairs to separate in meiosis I or sister chromatids to separate in meiosis II

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26
Q

What is gonadal mosaicism? I

A

When precursor germ line cells to ova or spermatozoa are a mixture of two or more genetically different cell lines (one is mutated the other is not)- certain sperm cells will be mutated

Individual is not affected as mutation not in somatic cells- however all gametes from mutated germ line is affected.

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27
Q

When does risk of gonadal mosaicism increase?

A

With increasing paternal age- more time for mutations

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28
Q

What does mitosis produce

A

2 diploid daughter cells that are genetically identical to parent cell.

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29
Q

What phases of the cell cycle make up interphase?

A

G1, S and G2

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30
Q

What is meiosis used for?

A

Production of gametes

31
Q

What does meiosis produce?

A

4 haploid daughter cells genetically different to the parent cell

32
Q

How is genetic diversity produced in meiosis I?

A

Prophase I- crossing over

Metaphase I- random assortment

33
Q

What is a multifactorial disease?

A

Disease due to genetic and environmental factors (e.g schizophrenia and diabetes).

An individual may have a genetic predisposition but am adverse environmental trigger is required for onset.

34
Q

Definition of genotype

A

Genetic constitution of an individual

35
Q

Definition of phenotype

A

Appearance of an individual (physical, biochemical and physiological) which results from interaction of genotype with the environment.

36
Q

Definition of allele

A

One of several alternative forms of a gene at a specific loci.

37
Q

What is the longest phase of the cell cycle?

A

Interphase

38
Q

What is the most common inheritance pattern for gonadal mosaicism?

A

X-linked or autosomal dominant

It’s more common in males

39
Q

What conditions is gonadal mosaicism observed in?

A

Osteogenesis imperfecta and duchenne muscular dystrophy

40
Q

Definition of locus

A

Position of gene/ DNA on the genetic map

41
Q

What is a wild type allele?

A

Non mutagenic alleles are termed wild types whilst pathogenic mutations / variants are carried on disease alleles

42
Q

What is consanguinity ?

A

Reproductive union between 2 relatives: descended from the same ancestor.

43
Q

Definitions of homozygous, heterozygous and hemizygous.

A

Homozygous: both alleles of a gene at a particular loci are the same.

Heterozygous: both alleles of the same gene at a particular loci are different

Hemizygous: only one allele of a gene is present at a particular locus.

44
Q

What are polymorphisms?

A

Frequent hereditary variations at a particular locus- they do not cause problems, the mutations do.

They can make you more / less efficient or more / less susceptible to a disease.

45
Q

Define autozygosity

A

Homozygous by descent

Inheritance of the same mutant allele through two branches of the same family

46
Q

Define penetrance

A

Proportion of people with a particular gene / genotype that show the expected phenotype.

47
Q

Difference between complete and incomplete

A

Complete: gene / genes for a trait are expressed in all the population.

Incomplete: genetic trait is only expressed in parts of the population.

48
Q

Definition of variable expression

A

Variation in clinical features (type and severity) between individuals with the same gene alteration.

49
Q

Define sex limitation

A

Expression of a particular characteristic is limited to one of the sexes.

50
Q

Term for a condition that manifested at birth

A

Congenital

51
Q

What is KNudson’s two hot hypothesis?

A

Gene mutations can be inherited OR acquired during a person’s life

  • sporadic cancers: 2 acquired mutations
  • hereditary cancers: 1 inherited and 1 acquired mutation
52
Q

4 examples of genetically inherited diseases

A

Down’s syndrome- non dysfunction chromosome 21
Cystic fibrosis
Huntington disease
Haemophilia

Individually rare but cumulatively enough to have genetic services

53
Q

4 examples of multifactorial diseases

A

Spina bifida
Cleft lip
Diabetes
Schizophrenia

Main cause of disease in developed countries

54
Q

4 environmental causes of disease?

A

Poor diet
Infection
Drugs
Accidents

Main cause of disease in third world countries and A&E

55
Q

What are the two Mendelian forms of inheritance?

A

Autosomal vs sex linked

Dominant vs recessive

56
Q

Give the typical features of autosomal recessive inheritance

A
  • Occurs in homozygous state (two copies of recessive allele must be present)
  • Affects males and females equally
  • If two parents are carries = 25% chance offspring will have disease and 50% chance they will be carriers.
  • Calculations at conception: healthy siblings have 2/3 chance of being carriers
  • Affected individuals in a single generation
  • Parents can be related e.g consanguineous (recessive conditions most common in these types of families.

When calculating risk probabilities of offspring, the affected child in disregarded.

57
Q

Give an example of an autosomal recessive condition

A

Cystic fibrosis:

  • most common autosomal recessive condition affecting white males in the UK
  • incidence of 1 in 25,000
  • Population carrier frequency is 1 in 25
58
Q

Definition of expressivity

A

Range of phenotypes expressed by a specific genotype

59
Q

Definition of anticipation

A

Where a genetic disorder affects successive generations earlier or more severely.

60
Q

Give the key features of autosomal dominant inheritance

A
  • Disease that manifests in heterozygous state
  • Affects males and females in equal proportions
  • Affected individuals in multiple generations
  • ONLY WAY TO PASS DISEASE FROM MALE TO MALE
  • 50% chance of offspring having the condition
  • Can appears to skip a generation but this is due to penetrance and variable expression
  • Example: Huntington’s disease
61
Q

Give the key features of X-linked inheritance

A
  • Caused by a mutation on the X chromosome
  • Usually affects females more than males
  • Affected males cannot pass mutation to son, all daughters of affected males are carries.
  • Males cannot be carriers
  • Usually inherited from unaffected mothers
  • X-linked dominant condition: Alports syndrome
  • X-linked recessive condition: Duchenne muscular dystrophy
62
Q

Define lyonisation

A

Process of X chromosome Inactivation

One of the 2 X chromosomes in randomly inactivated in early embryonic development

The X chromosome is inactivated to prevent women having twice as many gene products from the X chromosome as males

Only functional copy of the X chromosome

63
Q

What is an ideogram

A

A diagrammatic form of chromosome bands

The bands are numbered according to their distance from the centromere

64
Q

What is Mendel’s second law?

A
  • Law of independent assortment

- Alleles of one gene sort into gametes independently of alleles of another gene.

65
Q

Would an X-linked dominant condition be more common in males or females?

A

They occur twice as frequently in females as they do males.

66
Q

Is an x-linked recessive condition more common in males or females?

A

Males

67
Q

Define sex limitation

A

Both sexes have a particular gene but it’s expression is limited to only one of the sexes

68
Q

Which parent is all our mitochondrial DNA inherited?

A

Mother

69
Q

Stages in the production of a thin cell microscope slide

A
  • Tissue fixed in formalin
  • Samples embedded in paraffin
  • Fine slices mounted on microscope slide
70
Q

What does H&E stain

A

Haematoxyoin- stains nuclie and other acidic substances blue
Eosin- stains cytoplasm and extra cellular fibres pink

71
Q

Used of periodic acid schiff

A

Stains sugars magenta !

72
Q

Use of van giesan stain?

A

Stains elastic tissue brown !

73
Q

Use of trichrome stain?

A

To stain 3 different types of cell 3 different colours all within the same section

Most common = Masson’s trichrome

74
Q

Use of Alcian blue stain?

A

Stains mucins blue

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