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Pathophysiology > genetic > Flashcards

genetic Flashcards

1
Q

Structure of Deoxyribonucleic Acid (DNA)

A

-made up of nucleotides
-sugar, phosphate group, one of 4 bases ACGT
-arranged in double helix with hydrogen bonds in the middle

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2
Q

Chromosomes

A

threadlike DNA composed of
chromatin only visible during cell division
-humans have 23 pairs of chromosome
-entire set of human chromosomes is the human genome
-we also have non coding DNA called pseudo genes - genetic information that is not used or is edited out of mRNA before proteins are made.

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3
Q

Gene

A

-on a chromosome a short sequence of DNA that will be transcribed to premRNA then protein
-always found a fixed location (locus)
-introns are non coding portions that interpret sequences
-during RNA splicing introns -intervening sequences are removed and exons EXpressed

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4
Q

Alleles

A

-different versions of a gene found at the same loci causing different phenotype
-everyone has 2 copies of each gene so you can have 2 different or 2 same alleles
-homologous chromosomes are matching pair of chromosomes
-loci are alleles can be hetero or homo

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5
Q

Dominant gene

A

A gene whose effects are seen and is capable of masking the effects of
a recessive gene for the same trait (often represented by uppercase letters)

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6
Q

Codominance:

A

Both dominant genes are expressed. 2 or more genes that are dominant and when they appear together produce a combined effect in offspring e.g. blood type Group AB has both the A and the B antigens

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7
Q

Genetic carrier:

A

A person who carries a recessive gene but does not show its effects because it is masked by dominant gene

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8
Q

Hereditary Traits

Dominant genes/alleles

Recessive genes/alleles

Co-dominant genes:

A

Dominant genes/alleles: phenotype is always present

Recessive genes/alleles: phenotype is always masked by the Dominant allele and will only be expressed in the
HOMOZYGOUS state

Co-dominant genes: both alleles will express the phenotype

Traits can be physical attributes or hereditary diseases

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9
Q

How do we inherit genes

A

Inheritance is known as:
* Autosomal if the gene is found on chromosomes 1-22
* Sex-Linked if the gene is found on the X or Y chromosome

1 chromosome from each parent = 1 gene from each parent through meiosis dividing chromosomes into haploid gametes
➢Two potential alleles

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10
Q

Genetic Variation

what are autosomes

Normal variation among offspring is increased by:

A

autosomes-Twenty-two pairs of chromosomes. they are almost identical

the leftovers are called sex chromosomes and dont match

Normal variation among offspring is increased by:
Independent assortment of chromosomes during gamete formation
➢Crossing-over of genes between partners during meiosis.
-Meiosis produces gametes with 23 chromosomes each. When two gametes join they form a zygote with 46 chromosomes

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11
Q

Crossing-Over

A

-form of recomb
-genes from one location “cross over” to the same location on the matching gene and as the chromosome separates and gets back together each will pick up new genetic material from the other

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12
Q

Nondisjunction:

A

failure of a chromosome pair to separate
during gamete production, causing trisomy or monosomy in the offspring.

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13
Q

Aneuploidy -Numerical Abnormalities

A

-abnormal number of chromosomes.
-non modal chromosome amount either 1 extra -47 or 1 less -45. Happens in both autosomes and sex chromosomes

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14
Q

Down Syndrome: Trisomy 21

A

Chromosomal Disease
-extra copy of chromosome 21
-mental impairment
-structural defects- short hands/feet, heart disease, large tongue

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15
Q

Klinefelter Syndrome

A

Chromosomal Disease
-long legs, low intelligence, sterility , pulmonary disease
-two or more X with a Y so a man with womanly features

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16
Q

Turner Syndrome XO syndrome:

A

Chromosomal Disease
-nondisjunction of sex chromosome during gamete formation
-monosomy of sex chromosomes - XO genotype- affects women only one x chromosome is missing
- failure of sex organs to mature causing sterility, short stature, learning disorders but only in certain area like math but not reading

17
Q

Gene Mutation checkpoints
what happens if a cell is too damaged

A

cell either continues or undergoes apoptosis

G1- before S phase. Check to make sure cell is proper size and has correct proteins for synthesis. Cell growth checkpoint. Where spontaneous mutations are repaired
G2- DNA synthesis checkpoint which occurs during 2 phase before mitosis. checks to see if DNA has been replicated properly

cytokinesis is the physical process of division

if a cell is too damaged it will go through
senescence - dormancy
apoptosis
unregulated division causing a tumor

18
Q

what is a mutagen

A

-causes mutations that changes DNA structure , bases or alter pairings, they can distort the helix

Can be chemical
Alkylating agents (e.g. mustard gas)
➢Intercalating agents (e.g. ethidium bromide used in Molecular
➢Radiation: X-rays, UV light
➢Viruses

19
Q

Mutations in cells

somatic

germ line

A

SOMATIC mutations occur in non-gamete
cells that cause a mutated protein which can be passed through mitosis and cause disease like cancer

germ-line - spontaneous but it will get passed through meiosis and become hereditary

mutation can be beneficial, harmful or have no harm like albinism or color blindness

20
Q

Colour-blindness

A

-recessive x linked so a female carrier can have sons with color blindness
Red-green color blindness is sex linked but blue blindness affects both men and women as it is non sex linked

21
Q

➢Epigenetics

A

imprinting
science describing how offspring can have mutations that not passed down but environmental. for example diet or lifestyle that can turn the gene off or on. So like twins that are genetically predisposed to lung cancer but only the one that smokes gets it

22
Q

Mitochondrial Inheritance

A

-Inheritance of mDNA from mother ONLY
-mitochondria from sperm do not survive after ovum fertilization
-mDNA has genetic code only for enzymes in metabolic pathway that recharges ATP but this also increases potential for carrying mutations that cause disease

23
Q

Acquired versus Inherited

A

acquired - mutation in specific cells at some time in a persons life- skin cancer

inherited - occur during reproduction present throughout the persons life in every cell - Trisomy 21

24
Q

Cystic fibrosis:

A

Single-Gene Disease

recessive autosomal
-excessive sweating and mucus production affecting digestive and respiratory tracts

25
Q

Phenylketonuria (PKU)

A

Single-Gene Disease

recessive autosomal
-excess phenyl ketone in urine
-accumulation of phenylalanine in tissues = brain injury and death
-special diet can prevent accumulation of toxic levels of phenylalanine.

26
Q

Tay-Sachs disease (TSD)

A

Single-Gene Disease
recessive

-failure to make subunit for lipid processing enzyme hexosaminidase therefore causing lipid accumulation in the brain resulting in death by age 4

27
Q

Sickle Cell Disease

A

Single-Gene Diseases
abnormal HB production hb S instead of A - codominant but S is mutated allele
-beneficial mutation gone wrong the sickle cell TRAIT when heterozygous gives resistance to Plasmodium falciparum: the worst form of Malaria. However when homo the sickle cell disease is very painful causing hemolytic anemia
-Glutamic acid substituted for valines - missense mutation

Screening - sickledox
-sue one drop of blood with a reagent that lowers oxygen tension causing HbS cells to sickle
-HgB electrophoresis can be done as well to detect presence of abnormal hgB

-

28
Q

Hemophilia and types?

A

Hemophilia: lack of a clotting factor produced by the liver
Hemophilia A: factor VIII missing
Hemophilia B: factor XI missing

if you cant form proper clots then youve got a bleeding disorder

-testing done in coagulation bench to detect clotting factors - tests PT and APTT.
Start with most common tests and then add the factors

-Hemophilia is sex linked on X
-most are male
-if a carrier woman partners with a male hemophiliac then she can have two X -H genes

29
Q

Genemutation when causing disease

A

-mutations can occur due to lack of protein or abnormal protein production.
-if the mutagen alters the base and its then transcribed onto the mRNA then the whole codon is changed for the aa. Therefore protein structure and function are changed.

30
Q

POINT mutation

Silent:

Nonsense:

Missense:

Missense:

A
  • POINT mutation: single base substitution
  • Silent: codon codes for the same aa therefore no change
  • Nonsense: changes to a STOP codon, therefore shorter protein (due to fewer aa)
  • Missense: conservative: codes for aa with similar biochemical properties (e.g. hydrophobic, charge, etc.)
  • Missense: non-conservative: codes for aa with different biochemical properties
31
Q

Somatic Chromosome
Mutations

A

changes at the GENE level

Structural rearrangements of chromosomes:
➢Translocations -
➢Inversions -
➢Deletions
These usually cause cancer

32
Q

chromosomal translocation

A

➢Possible loss of genes
➢Possible fusion of genes
➢Possible production of fusion protein
➢Fusion protein may encourage cell-division or prevent apoptosis
➢ Philadelphia Chromosome in Chronic Myeloid Leukemia: Philadelphia chromosome or Philadelphia translocation Formation of a chimeric fusion gene- fusion hybrid protein

33
Q

Philadelphia Chromosome

A

Forms chimeric fusion gene BCR/ABL Normal ABL protein is a tyrosine kinase: that controls cell proliferation, apoptosis and differentiation.
BCR regulates cell growth.
So when they fuse they make a tyrosine kinase that cannot shut off - lots of proliferation and no apoptosis

34
Q

karyotype

A
  • chromosome photographs used to detect abnormalities
    -the paired chromosomes are collected during metaphase
35
Q

cytogenetics tests

A
  • showing chromosome banding in different colors
    -AT dark
    GC light

Chromosomes are identified by centromere position, length and banding pattern. They are scanned and arranged in a karyotype.
If there are structural changes - translocation
If there are abnormal numbers - trisomy

Pathophysiology (6 decks)

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