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Musculoskeletal system > Foundations of medicine Block 1 Week 2 > Flashcards

Foundations of medicine Block 1 Week 2 Flashcards

1
Q

Name the 4 basic tissue types ?

A

Nervous
Muscle
Epithelial
Connective

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2
Q

There are 3 main types of connective tissue ?

A
  • Connective tissue proper
  • Specialised connective tissue
  • Embryonic connective tissue
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3
Q

What are the two types of connective tissue proper ?

A

Loose
Dense

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4
Q

Describe loose connective tissue? (connective tissue proper)

Where is loose connective tissue proper found ?

A

More cells than fibres . Collagen is the most predominant fiber with moderate amounts of elastin. Sparse arrangement.

More ground substance

Found under skin and around organs

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5
Q

Describe dense connective tissue? (Connective tissue proper)

A

More fibres than cells

Less ground substance

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6
Q

What are the 3 types of dense connective tissue ?

A

Dense regular connective tissue:
Fibers are arranged in parallel for a unidirectional resistance to stress.
Typically found in tendons and ligaments

Dense irregular connective tissue
Irregular pattern of collagen and elastin means it can sustain tension under many different directions. Forms a 3D meshwork.
Typically found surrounding organs and joints.

Dense elastic connective tissue
Elastic fibers which are tightly packed which allow for stretch and recoil
This is found in the aorta.

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7
Q

Give 4 examples of specialized connective tissue:

A

Adipose

Blood

Cartilage

Bone

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8
Q

Describe adipose tissue ?

A

Made up of adipocytes that are filled with lipid droplets

There is only a small amount of ECM and very few collagen fibers keeping the cells together.

White adipose tissue and brown adipose tissue

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9
Q

Describe white adipose tissue ?

A

White adipose tissue: found in adults and is energy storing, protective ( cushions internal organs) and secretory. Distributed as parietal: Found embedded in the connective tissue proper, found primarily in the abdomen, thighs, hips and back.

Visceral : surrounds and supports the bodys organs

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10
Q

Describe brown adipose tissue ?

A

Brown adipose tissue: found in babies and is thermogenic ( heat production)

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11
Q

Describe blood ?

A

Made up of red blood cells, white blood cells, platelets and plasma.

Function: acts to transport gases, nutrients, waste and macromolecules.

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12
Q

Describe bone ?

A

Calcified ECM ( extracellular matrix) is responsible for its hard nature.

The cells are trapped within the calcifies bone matric

Osteon with concentric rings surrounding central canals.

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13
Q

Describe cartilage ?

A

Is avascular ( no blood vessels) as a result nutrients must diffuse across the ECM.

Chondrocytes are the cells found within cartilage ECM, they secrete small amounts of ECM to preserve structural integrity.

Chondrocytes produce cartiallage

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14
Q

What are the 3 types of cartilage ?

A

Hylaine cartilage
Elastic cartilage
fibrocartilage.

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15
Q

What is the process of going from DNA to RNA called ?
What is the process of going from RNA to protein called ?

A
  1. Transcription
  2. Translation
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16
Q

Which nucleic acids are found in purine bases (2 hexagon)?
Which nucleic acids are found in pyrimidine bases (1 heaxgaon) ?

A

1.adenine and guanine
2. cytosine, thymine, uracil

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17
Q

What are the sugars and bases in DNA ?
What are the sugars and bases in RNA ?

A
  1. Deoxyribose sugar and (A,C, G and T)
  2. Ribose sugar and (A, C, G and U).
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18
Q

What are some other roles of nucleotides (bases)?

A
  1. Energy carrier - ATP
  2. Signalling - cAMP, cGMP
  3. Enzyme co-factors - CoA, FMN, FAD, NAD, NADP
  4. Used to create RNA AND DNA
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19
Q

In which direction are polynucleotides read?

A

Polynucleotides are read in the 5’ 3’ direction.

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20
Q

Which bonds are between bases in DNA?
Which bonds are between the phosphate group and pentose sugar?

A
  1. Hydrogen bonds
  2. Phosphodiester bonds
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21
Q

How many base pairs of DNA is in the human genome ?

A

3 billion base pairs

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22
Q

Describe nuclear DNA ?
Decscribe mitochondrial DNA ?

A
  1. Is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest.
    linear, packed in discrete structures called chromosomes

accounts for the vast majority of the genome (3200 Mbp)

Mitochondrial DNA:

circular, 2-10 copies per mitochondrion

16,569 base pairs, encodes 37 genes

maternally inherited

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23
Q

How is DNA organised ?

A

DNA is wrapped around histones
The complex of DNA and associated proteins in the eukaryotic cells is know as CHROMATIN and makes up 80 -90 % of nuclear mass.

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24
Q

What is the nucleosome ?

A

DNA wound around histones forms the basic packaging unit of chromatin known as the nucleosome.

The nucleosome consists of two complete turns of DNA (146 bp), wound around a core of histone proteins.

Each nucleosome is separated by a linker region of DNA of variable length (20-60 bp).

The nucleosome gives ‘unpacked’ DNA a ‘beads on a string’ appearance.

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25
Q

What is Euchromatin ?

A
  • ‘unpacked’ beads on a string
  • is a lightly packed form of chromatin (DNA, RNA, and protein) that is enriched in genes, and is often (but not always) under active transcription.
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26
Q

What is Heterochromatin ?

A
  • ‘Packed’ 30nm fibres.
  • Adjacent nucleosomes packed together to form a chromatin fibre of 30nm diameter.
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27
Q

How many chromosomes does each Somatic (body ) cell contain ?

A
  1. 46 chromosomes
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28
Q

We carry 2 copies of each chromosome what is this called ?

A

homologous chromosome pairs

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29
Q

What is the stereotypic number, size and shape of chromosomes during metaphase called ?

A

Karyotype

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30
Q

When are chromosomes visible as a karyotype ?

A
  1. During metapahse chromosomes are visible as duplicated chromatids attached at the centreomere.
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31
Q

What is the cell cycle ?

A

The cell cycle is an ordered series of events that leads to division of a cell into two identical daughter cells.
The duration of a cell cycle depends on the cell type. In a fast dividing cell it is approx 24 hrs.

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32
Q

What is the normal karyotype for a female and male ?

A

Female: 46, XX
Male: 46, XY

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33
Q

What is the karyotype of Trisomy 21 ?

A

Trisomy 21 is also known as Downs syndrome

Female karyotype: 47, XX, +21
Male karyotype: 47, XY, +21

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34
Q

Define Mitosis ?

A

Mitosis is when the cell divides.

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35
Q

What is cytokineses ?

A

the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.

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36
Q

Describe phases of the cell cycle ?

A

G0 phase (resting stage): The cell has not yet started to divide. Cells spend much of their lives in this phase. Depending on the type of cell, G0 can last from a few hours to a few years. When the cell gets a signal to divide, it moves into the G1 phase.

G1 phase (interphase): During this phase, the cell starts making more proteins and growing larger, so the new cells will be of normal size. This phase lasts about 18 to 30 hours.

S phase (interphase): In the S phase, the chromosomes containing DNA are copied so that both of the new cells formed will have matching strands of DNA. The S phase lasts about 18 to 20 hours.

G2 phase (interphase): In the G2 phase, the cell checks the DNA and gets ready to start splitting into 2 cells. This phase lasts from 2 to 10 hours.

M phase (mitosis): In this phase, which lasts only 30 to 60 minutes, the cell actually splits into 2 new cells.

Cytokinesis - the cytoplasm splits

There are checkpoints to make sure the cell cycle is happening correctly. These happen at different points.

Metaphase checkpoint.
G1 checkpoint.
G2 checkpoint
(G=gap, S=synthesis, M=mitosis)

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37
Q

Describe the stages of mitosis ? (prophase and prometaphase)

A

Prophase:

Chromosome condensation

Dispersal of nucleoli

Separation of centrosomes and formation of mitotic spindle

Prometaphase:

Fragmentation of the nuclear envelope

Attachment of spindle MTs to centromeres

Chromosomes start to move towards cell centre (congression)

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38
Q

Describe the stages of mitosis ? (Metaphase to telophase )

A

Metaphase
1.Chromosome alignment at metaphase plate

Anaphase:
Chromosomes (chromatids) move to opposite cell poles

Telophase:
Chromosomes uncoil

Nucleoli develop and fuse

Disassembly of spindle

Re-formation of the nuclear envelope

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39
Q

What is the function of the mitotic spindle ?

A

The mitotic spindle is formed from microtubules and is organised from the two centromeres which migrate to the opposite poles during mitosis.

The microtubules attach to the centromere of chromosomes via the kinetochore.

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40
Q

What is 5FU ?

A

Fluorouracil, which is often called 5FU, is a chemotherapy therapy drug used to treat different cancers including breast, bowel, skin, stomach, oesophageal (gullet), and pancreatic cancer.

Brand name: Adrucil

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41
Q

All nucleus contain the same genome but all cells look different. This is because different cells express different genes. Its all about gene expression.

A
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42
Q

Define Gene ?

A

A unit of heredity that is transferred from a parent to the offspring and is held to determine some characteristic of the offspring

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43
Q

Detection of which which chemical in circulation is a highly sensitive diagnostic marker of myocardial infarction ( better than ECG) ?

A

Detection of Creatine Kinase in circulation is a highly sensitive diagnostic marker of myocardial infarction (better than ECG

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44
Q

What percentage of our genes make proteins ?
What is a gene that codes for a protein called ?

A
  • 2% of our genes make proteins
  • Genes that code for a protein are called protein - coding gene.

A protein coding gene contains all the nucleotide sequence necessary to produce a mature messenger RNA (mRNA).

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45
Q

How much of our genome is actively used (transcribed) in the form of non-protein coding RNA ?

A
  • Nearly half of our genome is actively used ( transcribed ) in the form of non-protein -coding RNA.
46
Q

Overview of gene expression ?

A
47
Q

When and why does gene transcription take place ?

A

When and where a gene is transcribed is under the control of the promoter and regulatory sequences of the gene.

A gene is transcribed by RNA polymerase.

Proteins called “transcription factors” bind to the promoter and regulatory sequences of the gene and influence gene transcription.

The combination of transcription factors bound to the promoter and regulatory sequences modulates the activity of RNA polymerase and determines where, when and at what levels a gene is transcribed.

48
Q

Describe splicing of a pre-mRNA ?

A

The exons and introns constitute the parts of a gene that are transcribed.

Both exons and introns constitute the immature pre-mRNA.

During the maturation of the pre-mRNA to form a mature mRNA the intron sequences form a loop structure and are excised in association with a complex called the spliceosome. This is called splicing.

The protein coding region is contained within the exons.

49
Q

Describe the modification to pre-mRNA after splicing ?

A

In addition to splicing the primary transcript is modified at its 5’ and 3 ends’. These modifications are important for efficient translation and stabilisation of the message

Capping: A cap structure (7-methyl guanosine) is added to the 5’ end of mRNAs shortly after transcription is initiated.

Polyadenylation: At the 3’ end of the RNA the enzyme poly-A polymerase adds 100 to 300 Adenine residues to form a poly-A tail.

50
Q

Describe how Non-coding RNAs destabilise mRNAs ?

A

The levels of mature mRNA are further regulated after transcription and before translation by non-coding RNAs.

Examples include microRNAs, long non-coding RNA

microRNAs reduce levels of mRNAs by destabilising them and inhibiting initiation of their translation.

The effect of microRNAs on mRNAs is called RNA-induced silencing.

51
Q

Describe mRNA translation ?

A
  • The transformation of genetic information (bases) into proteins (amino acid sequences) is based on the genetic code.

-The coding region of an mRNA is read in triplets of bases known as codons. Each codon corresponds to an amino acid or a translation stop signal (stop codon).

-The genetic code is a degenerate code. There are only 20 amino acids and three stop codons. Most amino acids are coded for by more than one codon.

  • Knowing the nucleotide sequence of an mRNA allows us to derive the amino acid sequence of its protein product.

-The formation of the peptide chain is catalysed and orchestrated by ribosomes in the cytoplasm.

-Ribosomes associate with a number of regulatory proteins, including initiating and releasing factors.

-The sequence of codons from the AUG (initiator – methionine) to the terminating stop codon is known as the open reading frame or ORF.

52
Q

Describe ribosomes in relation to genes ?

A

-Ribosomes are high molecular weight structures composed of protein and RNA.

-Ribosomes are composed of two sub-units.

-The small ribosomal sub-unit binds tRNA and mRNA.

-The large ribosomal sub-unit catalyzes the addition of amino acids to the extending peptide chain.

53
Q

How is translation initiated ?

A

Translation is initiated at an AUG codon which codes for the amino acid methionine

Small ribosomal sub-unit scans along mRNA from 5’ end

The small and large ribosomal sub-units assemble at the initiator and begin to translate the mRNA into protein

AUG - AND U GO

54
Q

Explain antibiotics which are translation inhibitors ?

A

Many antibiotics are inhibitors of bacterial protein synthesis.

Antibiotics make use of the structural and functional differences between eukaryotic and prokaryotic ribosomes

Tetracycline blocks entry of tRNAs into ribosome complex.

Chloramphenicol blocks addition of new amino acids into peptide chain.

Tetracycline is used to treat infections caused by bacteria including pneumonia and other respiratory tract infections; ; certain infections of skin, eye, lymphatic, intestinal, genital and urinary systems; and certain other infections that are spread by ticks, lice, mites, and infected animals.

Chloramphenicol is a broad spectrum antibiotic that is effective against a variety of susceptible and serious bacterial infections but is not frequently used because of its high risk of bone marrow toxicity.

55
Q

What happens post translation ?

A

Following translation proteins are further modified and acquire three dimensional structures.

Common post-translational modifications include glycosylation (addition of sugar residues) and phosphorylation (addition of phosphate groups).

Misfolded proteins are ubiquitinated (addition of a small chemical moiety called ubiquitin) and degraded.

The function and localisation of proteins in a cell is determined by their structure and post-translational modification.

56
Q

Describe protein localisation ?

A

The localisation of a protein in a cell is determined by its structure and post-translational modifications.

Many proteins that are found in the nucleus contain a nuclear localisation signal peptide in their sequence.

In other cases only the phosphorylated form of a protein can be transported to the nucleus.

Proteins that are either secreted from the cell or are inserted into cellular plasma membrane have an endoplasmic reticulum (ER) signal sequence or peptide at their amino terminus.

Membrane associated and secreted proteins which have passed into the ER are trafficked in vesicles to the Golgi apparatus, where they are further modified.

57
Q

Describe what the arms of a chromosome mean ?

A
58
Q

Describe a metacentric chromosome ?
Descibe a submetacentric chromosome ?
Describe a acrocentric chromosome ?

A

Metacentric chromosome (1):
Centomere is in the centre

p and q arms are equal in length

eg chromosome 1

Submetacentric chromosomes (4):
Centomere is slightly offset from the centre

eg chromosome 4

Acrocentric chromosome (13) :
Centomere is severely offset from the centre

p arm is very short

eg chromosome 13

59
Q

How do we see cells on a microscope at metaphase ?

A

This is called Chromosome (metaphase) spread.
Chromosomes are visible during metaphase of cell division

Arrest the cells in metaphase by treatment with colcemid, which disrupts the cell spindle

Fix and drop the cell suspension onto a microscope slide

60
Q

Describe Giemsa staining of chromosomes ?

A

Giemsa staining of chromosomes (G banding)

Laboratory protocols result in dark and light banding patterns

Dark bands correspond to condensed A, T rich (gene poor) regions of the chromosomes.

G-banding, G banding or Giemsa banding is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is the most common chromosome banding method. It is useful for identifying genetic diseases through the photographic representation of the entire chromosome complement.The metaphase chromosomes are treated with trypsin (to partially digest the chromosome) and stained with Giemsa stain. Heterochromatic regions, which tend to be rich with adenine and thymine (AT-rich) DNA and relatively gene-poor, stain more darkly in G-banding. In contrast, less condensed chromatin (Euchromatin)—which tends to be rich with guanine and cytosine (GC-rich) and more transcriptionally active—incorporates less Giemsa stain, and these regions appear as light bands in G-banding. The pattern of bands are numbered on each arm of the chromosome from the centromere to the telomere. This numbering system allows any band on the chromosome to be identified and described precisely.

61
Q

Define genetic Polymorphism ?

A

Locus: In genetics, a locus is a specific, fixed position on a chromosome where a particular gene or genetic marker is located.

A gene is said to be polymorphic if more than one allele occupies that gene’s locus within a population.

In addition to having more than one allele at a specific locus, each allele must also occur in the population at a rate of at least 1% to generally be considered polymorphic.

The majority of polymorphisms are silent, meaning they do not alter the functionGene allele can have two or more variants

Most genes are ‘polymorphic’

Variants can be classified as common (population frequency ≥1%)

or rare (population frequency <1%)

Geographical differences in allele frequency or expression of a gene.[3] Some polymorphisms are visible. For example, in dogs the E locus can have any of five different alleles, known as E, Em, Eg, Eh, and e.[4] Varying combinations of these alleles contribute to the pigmentation and patterns seen in dog coats.

62
Q

Define microsatellite (aka str) ?

A

Microsatellite, as related to genomics, refers to a short segment of DNA, usually one to six or more base pairs in length, that is repeated multiple times in succession at a particular genomic location. These DNA sequences are typically non-coding.

63
Q

Define genetic linkage ?

A

Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction

64
Q

What are having two identical alleles of a particular gene or genes ?

A

Homozygous e.g ( alleles B2 and B2)

65
Q

What is having two different alleles of a particular gene or genes called ?

A

Heterozygous e.g. (alleles A7 and A9)

66
Q

Describe SNR ( single nucleotide variants) ?

A

Occur throughout an individual’s DNA sequence

Commonly found in non-coding DNA but can occur in exons

Approximately 1 SNV per 1000 nucleotides (4-5 million SNV per individual’s genome)

A DNA sequence variation that occurs when a single nucleotide (adenine, thymine, cytosine, or guanine) in the genome sequence is altered. Single nucleotide variants may be rare or common in a population

67
Q

Describe PCR and the detection of genetic ‘polymorphisms’ ?

A

The polymerase chain reaction is a method widely used to rapidly make millions to billions of copies of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it to a large enough amount to study in detail.

Polymerase chain reaction (PCR) generates millions of copies of a specific DNA sequence in a few hours

PCR can be used on minute amounts of starting DNA
Widely used to generate sufficient DNA prior to detection & identification of DNA variants

68
Q

Name 2 types of genetic ‘polymorphism’ ?

A

Short tandem repeats ( STR)
Single nucleotide variants ( SNV)

Polymorphism, as related to genomics, refers to the presence of two or more variant forms of a specific DNA sequence that can occur among different individuals or populations. The most common type of polymorphism involves variation at a single nucleotide

69
Q

Describe STR ( short tandem repeats) ?

A

Simple repeated DNA sequence motifs (also known as microsatellites)

‘Length polymorphisms’, e.g.

dinucleotide: (CA)(CA)(CA)(CA)(CA)(CA)

trinucleotide: (GCC)(GCC)(GCC)(GCC)(GCC)

tetranucleotide: (AATG)(AATG)(AATG)(AATG)

Many possible alleles (highly ‘polymorphic’)

Genome wide, but mostly located in

non-coding regions

70
Q

Why is the prevelnace of inherited disorders important ?

A
  • To see the risk for the individual
  • Risk of developing the disease
    -Risk of being a carrier of the disease

Family history helps determine this

71
Q

Whys is it important to know about the inheritamce of genetic disorders ?

A

Prevention
Genetic counselling
Risk for other family members
Risk for unborn child
Preventative surgery and treatment

72
Q

What causes genetic variation?

A

Adaption and evolution
Natural selection (gene pool)

73
Q

Vast majority of genetic variation has no significance and some are disease associated.

A
74
Q

By which mechanism does PCR take place?

A

Exopnential amplification x35-40

75
Q

What is another name for short term repeats ?

A

Microsatellites

76
Q

What does Allele A7 or Allele A9 mean ?

A

A9 - allele with 9 repeats
A7 - allele with 7 repeats

77
Q
A

Because of genetic redundancy. Many amino acids have 3 triplets that give rise to the same amino acid. So a change in the codon may not result in a chanage in the amino acid.

Even if a change did happen. This change be insignigicant and may not ahve a bif impact on that protein.

78
Q

RFLP ?

A

first type of SNV
and also acts as a recognition site for restriction enzyme

Restriction fragment length polymorphism (abbreviated RFLP) refers to differences (or variations) among people in their DNA sequences at sites recognized by restriction enzymes. Such variation results in different sized (or length) DNA fragments produced by digesting the DNA with a restriction enzyme. RFLPs can be used as genetic markers, which are often used to follow the inheritance of DNA through families.

79
Q

What is the coding and non coding regions of genes called ?

A

Introns - non coding regions
Exons - coding regions

Pre-mRNA contains introns and exons. Splicing happens after this has occured.

Splicing coverts pre-mRNA into functional mRNA.

80
Q

The genetic code is degenerate. What does this mean ?

A

It means more than one triplet can code for the same amino acid. Infact most amino acids can be coded by 4 triplets.

81
Q

What does it mean when you say genetic code is universal ?

A

The same codons will code for the same amino acids across all organisms.

82
Q

What is the start triplet for a polypeptide ?

A

AUG which codes for methionine

83
Q

What are the stop codons for a polypeptide ? (there are 3)

A

UAA
UAG
UGA

84
Q

What are chromosome G banding patterns ?

A

Banding patterns are patterns of light and dark transverse bands on chromosomes. The light and dark bands become apparent by staining the chromosome with a chemical solution and then viewed under a microscope. These bands describe the location of genes on a chromosome.

Identification of chromosomes:
- Chromosome length
- Chromosome structure ( centromere location, p - arm, q -arm)
- Normal banding pattern of each chromosome.

Light bands represent early replicating regions, rich in guanine and cytosine nucleotides. Dark bands represent late replicating regions, rich in adenine and thymine nucleotides.

85
Q

Describe chromosome banding patterns - gene location ?

A

The pattern of bands are numbered on each arm of the chromosome from the centromere to the telomere. This numbering system allows any band on the chromosome to be identified and described precisely. The reverse of G‑bands is obtained in R‑banding. Banding can be used to identify chromosomal abnormalities, such as translocations, because there is a unique pattern of light and dark bands for each chromosome.

86
Q

Describe fluorescent karyotyping ?

A
87
Q

What are the 4 chromosomal structural abnormalities that can be detected in a karyotype

A
  • Duplication
  • Inversion
  • Deletion
  • Insertion
  • Translocation
88
Q

What is Klinefelter syndrome ?

A

Males are born with extra X chromosome.

47, XXY
Sex chromosome abnormality
Numerical abnormality

Klinefelter syndrome (sometimes called Klinefelter’s, KS or XXY) is where boys and men are born with an extra X chromosome.

Klinefelter syndrome may adversely affect testicular growth, resulting in smaller than normal testicles, which can lead to lower production of testosterone. The syndrome may also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone has the same signs and symptoms.

Most men with Klinefelter syndrome produce little or no sperm, but assisted reproductive procedures may make it possible for some men with Klinefelter syndrome to father children.

89
Q

What is Turner Syndrome ?

A

Turner syndrome, a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing.

  • Numerical abnormality
  • Sex chromosome abnormality
  • Monosomy X
  • 45, X

In childhood, teens and adulthood
The most common signs in almost all girls, teenagers and young women with Turner syndrome are short stature and ovarian insufficiency due to ovarian failure. Failure of the ovaries to develop may occur at birth or gradually during childhood, the teen years or young adulthood. Signs and symptoms of these include:

Slowed growth
No growth spurts at expected times in childhood
Adult height significantly less than might be expected for a female member of the family
Failure to begin sexual changes expected during puberty
Sexual development that “stalls” during teenage years
Early end to menstrual cycles not due to pregnancy
For most females with Turner syndrome, inability to conceive a child without fertility treatment

90
Q

What is downs syndrome ?

A
  • Numerical abnormality
  • 47, XX, +21
  • 47, XY, +21
  • Also known as Trisomy 21
  • Autosome abnormality
  • Increased risk with maternal age.
  • Prenatal diagnosis
91
Q

What is NIPT ?

A

Down syndrome screening by NIPT
NIPT is a blood test that is more accurate than the first pregnancy screening test. It’s offered to women who are carrying a baby identified from previous screening tests as having a higher chance of having either Down’s syndrome, Edwards’ syndrome, or Patau’s syndrome. No screening test is 100% accurate.

92
Q

What is NIPT ?

A

Down syndrome screening by NIPT
NIPT is a blood test that is more accurate than the first pregnancy screening test. It’s offered to women who are carrying a baby identified from previous screening tests as having a higher chance of having either Down’s syndrome, Edwards’ syndrome, or Patau’s syndrome. No screening test is 100% accurate.

93
Q

Describe how many chromosomes are in a sperm, egg and zygote ?

A
  • Egg ( 23 chromosomes) (haploid)
  • Sperm ( 23 chromosomes ) ( haploid )
  • Zygote ( 46 chromosomes ) ( diploid)
94
Q

Normal inheritance ?

A
95
Q

Define how base changes in DNA lead to changes in protein?

A

Triple bases know as codons code for specific amino acids. Amino acids join together to make a specific protein. If there is a non-functional amino acid in the protein it is possible it could stop that protein form functioning correctly if at all.

It is possible that the amino acid that was coded wrong was degenerate. Often one amino acid can be coded for by more than one triplet. So it could be that the change in bases did not change the amino acid in that protein chain.

96
Q

What are the 3 types of changes base substitutions cause ?

A

Base substitutions - (substituting once base for another). Only a single nucleotide (base) is changed so one codon is affected. Although a base substitution only alters a single codon in a gene, it can have a significant effect on protein production. Base substitutions can lead to 3 subcategories of mutation.

Missense mutations: in which altered codon leads to the insertion of an incorrect amino acid into a protein molecule during translation.

Nonsense mutation: Altered codon prematurely terminates synthesis of a protein molecule.

Silent mutation: altered codon codes for the same amino acid as unaltered codon.

97
Q

Diseases and medicines of the cell cycle.
Name some cytotoxic agents ( chemotherapy) for cancer ?

A
  • FEC ( Fluorouracil (5FU), Epirubicin, Cyclophosphamide) for breast colon and other cancers.
  • Methotrexate for various cancers ( and autoimmune diseases)
  • Vinblastine and paclitaxel for various cancers including breast.

5FU: inhibits thymidylate synthase, methotrexate inhibits dihydrofolate reductase; interfere with DNA replication by blocking synthesis of thymine.

Cyclophosphamide: alkylating agent. Alkylates guanine, causes DNA crosslinks, interferes with DNA replication. Highly toxic and theratogenic.

Epirubicin: intercalating agent, blocks replication and transcription, damages DNA

98
Q

Diseases and medicines of the cell cycle.
Name some cytostatic for autoimmune disease ?

A
  • Cyclophosphamide for synthetic lupus erythematosus

Cyclophosphamide: alkylating agent. Alkylates guanine, causes DNA crosslinks, interferes with DNA replication. Highly toxic and theratogenic.

99
Q

Diseases and medicines of the cell cycle.
Name some immunosuppressants for transplantation ?

A

Cyclosporin
Tacrolimus
Sirolimus during renal trasnplantation.

Cyclosporin: binds cyclophilin, inhibits calcineurin; complex signalling that blocks transcription of certain genes and lowers activity of T-cells

Tacrolimus, sirolimus: inhibit calcineurin; complex signalling that blocks transcription of certain genes and lowers activity of T-cells
(Calcineurin is a calcium-binding protein; calcium necessary to activate T cells)

100
Q

How do we turn DNA to RNA DNA as a template ?

A
  • RNA polymerase makes an RNA copy of the sense DNA strand using the antisense DNA strand as the template.
    RNA polymerase moves along the template in a 3’ to 5’ direction and adds nucleotides to the 3’ end of the growing RNA chain (the RNA grows 5’ to 3’).
101
Q

If a SNV occurs in an exon and alters the amino acid sequence, this may affect the protein function. What effects could this have ?

A
102
Q

How do we use STR for genetic fingerprinting ?

A

The most common type of DNA profiling today for criminal cases and other types of forensic uses is called “STR” (short tandem repeat) analysis. Using DNA to distinguish between two individuals is a tricky matter, because close to 99.9 percent of our DNA is the same as everybody else’s DNA.

Analysis of DNA length

Many alleles (e.g. 1-8) per STR (highly ‘polymorphic’)

Current laboratory methods can analyse multiple STR simultaneously

Provide an unique pattern (fingerprint) for forensics,
paternity testing, etc.

Short tandem repeats (STRs) are short repeated sequences of DNA (2–6 bp) that account for approximately 3% of the human genome (Lander et al., 2001). The number of repeat units is highly variable among individuals, which offers a high power of discrimination when analyzed for identification purposes

103
Q

How do we use a RFLP to screen for sickle cell disease or trait ?

A

Restriction fragment length polymorphism (RFLP) is used to detect sickle cell disease based on restriction enzymes, which remove the recognition site at the βs mutated gene

104
Q

What is normal genotype ?
Sickle cell trait genotype ?
Sickle cell disease genotype ?

A
  1. AA
  2. AS
  3. SS
105
Q

How does human variation arise ?

A

Arises via recombination during meiosis

106
Q

Describe the human genome project ?

A

Its the DNA sequence of the entire human genome.

Completed in 2003 and identified approx. 30,000 human genes.

Has enabled the study of gene function, disease - associated genes and ‘polymorphisms’ / mutations.

107
Q

What is the Hardy-Weinberg equation ?

A

The Hardy-Weinberg equation is a mathematical equation that can be used to calculate the genetic variation of a population at equilibrium.

The Hardy - Weinberg principle is a mathematical model which can be used to predict the allele frequencies within a population.

p2 + 2pq + q2 = 1
p2 = dominant homozygous frequency (AA)
2pq = heterozygous frequency (Aa)
q2 = recessive homozygous frequency (aa)

108
Q

What factors will cause genetic variation will remain constant and evolution will not occur ?

A
  • No migration
  • no natural selection
  • an infinite population size
  • random mating
  • no mutation
109
Q

What are the assumption made when calculating hardy weinberg ?

A
  • No migration
  • no natural selection
  • an infinite population size
  • random mating
  • no mutation
110
Q

What are the causes of genetic variation in a population ?

A
  • gene flow
  • non-random mating
  • mutation
  • genetic drift
  • natural selection
111
Q

Cystic fibrosis hardy weinberg ?

A

Musculoskeletal system (29 decks)

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