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Flashcards in IMMS: Week 1 Deck (115):
1

Describe the structure of DNA

Double helix which complementary base pairing (A-T + G-C) -> nucleosomes -> supercoils -> chromosomes

2

How many chromosomes are there in an individual

46

3

What is an autosomal chromosome

One that is not sex-determining

4

What are the sex chromosomes in males and females

Males - XY and Females - XX

5

What is a karyotype

The number and appearance of a chromosome in a cell, arranged in order of size

6

How are chromosomes arranged in a karyotype

Pair 1 is the LARGEST, pair 22 is the SMALLEST, sex pair is 23

7

How many base pairs does each DNA duplex have

10^7 base pairs

8

How many genes do we have

22,000

9

Describe the arms of a chromosome

Each has a p (small) and a q (long) arm

10

What is mitosis

The division of a parent cell into two identical diploid daughter cells

11

What is DNA not in replication called

chromatin

12

What is DNA during replication called

Chromosomes

13

What is DNA following replication called

Chromatids

14

What stage of the cell cycle do we have to be in so mitosis can occur

Interphase

15

What is the longest phase of the cell cycle

Interphase

16

What happens in G1

No visible activity:
Rapid Growth
Normal Metabolic Function
New Organelles produced
Protein synthesis of those involved in spindle formation

17

What happens in synthesis

DNA doubles through DNA replication
Histone proteins double through protein synthesis
Centrosome replication

18

What happens in G2

Chromosomes condense
Energy stores accumulate
Mitochondria and centrioles double

19

What happens in prophase

Chromatin condenses into chromosomes
Centrosomes nucleate microtubules and move to opposite poles of the nucleus

20

What happens in metaphase

Chromosomes line up along the equatorial plane

21

What happens in anaphase

Sister chromatids separate and are pushed to opposite poles of the cells, centromere first as spindle fibres contract

22

What happens in telophase

Nuclear membrane forms
Chromosomes unfold into chromatin
Cytokinesis begins

23

What happens in cytokinesis

Cell organelles are distributes evenly across the two daughter cells

Cytoplasm divides

24

What is Down Syndrome

An extra chromosome at 21 (trisomy 21)

25

How can we tell on histological slides if a cell is undergoing mitosis

Dark nuclei and if the nuclei are not all the same size

26

Is meiosis a cycle?

No

27

What is the product of meiosis

4 haploid daughter cells which are distinct from each other and the parent cell

28

Where does crossing over of sister chromatids occur

meiosis 1 when chromosomes pair up into homologous pairs

29

Where does random assortment of chromosomes occur

In metaphase 1

30

What is the product of oogenesis

One egg cell and two polar bodies

31

Define non-disjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division

32

Name the two types of non-disjunction

Failure of separation of homologous chromosomes - meiosis I
Failure of sister chromatids to separate - meiosis II

33

What condition can this result in

Down Syndrome

34

Define Gonadal mosaicism

When precursor germline cells are a mixture of two or more genetically identical cell lines

One cell line is normal, the other is mutated

35

How can incidence of gonadal mosaicism increase

Increasing paternal age

36

Is gonadal mosaicism more common in males or females

Males

37

Is the parent also affected with gonadal mosaicism. Explain your answer

No because it results from mutation of the germline and not via inheritance

38

What inheritance pattern is usually seen with gonadal mosaicism

Autosomal dominant or X-linked

39

How common are genetic diseases

Not very rare but enough for us to make services which tailor to these conditions

40

Four examples of genetic diseases

Huntingtons
Cystic Fibrosis
Downs Syndrome
Haemophilia

41

What are multifactorial diseases

A combination of genetic and environmental factors

42

What is the main type of disease affecting developed countries

Multifactorial

43

Four examples of multifactorial diseases

Diabetes
Spina Bifida
Cleft Lip
Schizophrenia

44

What is the main cause of disease in third world and A&E

Environmental

45

What chromosomes are autosomal

1-22 (No sex chromosome)

46

What is a locus

The position of a gene/DNA on the genetic map

47

What is a genotype

Genetic constitution of an individual

48

What is a phenotype

Appearance of an individual which results from the interaction with the environment and genotype

49

What is an allele

One of several alternative forms of a gene at a specific locus

50

What is polymorphism

Frequent hereditary variations at a locus that do not cause problems.

51

How can polymorphisms affect you

Makes you more/less efficient or make you more/less susceptible to disease

52

Define consanguinity

Reproductive union between two relatives

53

Define autozygosity

Homozygous by descent (inheritance of the same mutant allele through two branches of a family tree)

54

Define homozygous

Both alleles at a specific locus are the same

55

Define heterozygous

Alleles at a locus are different

56

Define hemizygous

Describe that are carried on an unpaired chromosome (refers to X chromosome on a male)

57

Define penetrance

Proportion of people with a gene/genotype who show the expected phenotype

58

Define complete penetrance

Gene or genes for the trait are expressed in all the population

59

Define incomplete penetrance

Gene or genes for the trait are expressed only in parts of the population

60

Define variable expression

Variation in clinical features (type and severity) of a genetic disorder between individuals with the same gene alteration

61

Define sex limitation

Expression of a particular characteristic limited to one of the sexes

62

Define a multifactorial condition

Due to a combination of genetic and environmental factors

63

Define late-onset

Condition that hadn't manifested itself at birth

64

Define autosomal dominant

A disease that only manifests itself in the heterozygous state

65

Why can both parents be unaffected by a disease even if the son has it (3 reasons)

1. Gonadal mosaicism
2. Variable (incomplete) penetrance
3. Only way to pass it is from male to male

These are all seen with autosomal dominant conditions

66

Define autosomal recessive

A disease that manifests itself in the homozygous state only.

67

What is the chance of an offspring getting the disease if its autosomal recessive

25%

68

What is the chance of offspring being a carrier if its an autosomal recessive disease

50%

69

What is the chance of a healthy sibling being a carrier

2/3

70

What is the most common autosomal recessive disease in whites

Cystic Fibrosis

71

Does cystic fibrosis have complete or variable penetrance

Variable

72

Incidence of cystic fibrosis in the UK

1 in 25,000

73

Define X-Linked inheritance

Caused by a mutation in genes on the X-chromosome

74

Can an X-linked disease be passed on from father-to-son? and why?

No, never not even carriers

Because sons always get their X chromosomes from their mother

75

What are all daughters from an affected male (X-Linked disease)?

Carriers

NOTE: All males will be unaffected

76

What gender are X-linked disorders usually transmitted through

Females

77

Define lyonisation

The process of X chromosome inactivation

78

When is X chromosome inactivated

During embryological development

79

Why is the X chromosome inactivated during lyonisation

Prevents them from having a double number of X chromosome gene products compared to males

ONLY ONE X chromosome will be functional

80

What is a BARRBODY

Inactive X chromosome which is packaged in heterochromatin

81

What is the result of packaging an X-chromosome into heterochromatin

Prevents it from being transcripted

82

What is heterochromatin

Chromosome material of greater density than normal chromosome. Here the activity of genes are suppressed

83

What is imprinting (non-mendelian)

For some genes only 1 out of 2 alleles are active, the other is inactive (could be either that the maternal or paternal allele is inactive)

84

What is Knudson's 2-hit hypothesis

Gene mutations may either be inherited or acquired during a person''s life

85

What causes a sporadic cancer

2 acquired mutations

86

What causes hereditary cancers

1 inherited mutation + 1 acquired mutation

87

What is an 'ideogram'

Diagrammatic form of chromosome bands, bands are numbered according to distance to the centromere

88

What is the mendelian classification of genetic disease

Autosomal dominant/recessive or X-linked

89

What is a non-traditional genetic disease

Mitochondrial (all mitochondria is inherited by the mother), imprinting or mosaicism

90

What is a square in a genetic pedigree

Square = male
Circle = Female

91

What is epithelia needed for

Protection, absorption and secretion

92

What are four examples of supporting tissues

Blood, tendons, bones and cartilage

93

What are three types of muscle

Smooth, skeletal and heart

94

What does haematoxylin stain

Acids blue

95

What does eosin stain

Alkaline pink

96

What substances does haematoxylin stain

Cell nuclei and RNA blue

97

What does eosin stain

Cytoplasm and colloidal proteins pink

Keratin - Orange/red

ECF

98

Do water extra-cellular jelly and fat stain

No

99

What does Alcian Blue stain

GAG rich structures blue

Goblet cells blue

Mast cell granules blue

Stain cartilage matrix blue

100

What does iron haematoxylin stain

Nuclei and elastic fibres black

101

What does PAS stain

Hexose sugars (e.g. goblet cell mucous cartilage matrix, glycogen, basement membrane and glycocalyx) pink

102

What does touluidine blue stain

Nuclei, ribosomes and cytoplasm dark blue

Cartilage matrix and mast cell granules pale blue

GAG bright purple

103

Role of the nucleus

Houses DNA as chromatin within the nucleolus

Nucleolus produces RNA

104

Role of the mitochondria

Site of oxidative phosphorylation

Double membrane (highly folded inner)

105

What happens in the outer membrane of the mitochondria

Lipid synthesis and fatty acid metabolism

106

What happens in the inner membrane of the mitochondria

Respiratory chain (electron transport) ATP production

107

What happens in the mitochondrial matrix

Krebs' cycle

108

What take place in the mitochondrial intramembranous space

Nucleotide phosphorylation

109

Role of the RER

Site of protein synthesis

110

Role of SER

Site of membrane lipid synthesis

Processes and stores synthesised proteins

111

Role of the cis golgi

Receives SER vesicles and phosphorylates proteins

112

Role of medial golgi

Modifies products by adding sugars (to form oligosaccharides) to lipids and peptides

113

Role of the trans golgi network

Proteolysis of peptides into active forms and sorting of molecules into vesicles which bud from the surface

114

Where is the golgi apparatus located

Close to the cell nucleus

115

Can I see the golgi apparatus in most cells?

No, but seen clearly in plasma cells