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BIOL 2311 > Chapter 13- Genes, Chromosomes, and Human Genetics > Flashcards

Chapter 13- Genes, Chromosomes, and Human Genetics Flashcards

1
Q

What disease do Mickey Hayes and Fransie Geringer have what disease?

A

Progeria- a genetic disease that causes premature aging.

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2
Q

What is progeria?

A

A genetic disease that causes premature aging.

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3
Q

What is the error gene that causes progeria?

A

The error is in the gene Lamin A, one of the lamin proteins that reinforces the inner surface of the nuclear envelope in animal cells

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4
Q

Children from progeria die from diseases of old age at roughly at the age of ___

A

13

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5
Q

What is the chance of developing progeria?

A

1/20 million births

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6
Q

Progeria is also called this

A

Hutenion-Gilford Syndrome

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7
Q

Important discoveries in genetics were made in the “fly room” where flies aka drosophila melanogaster were cultivated at Columbia U in 1909 by ____. What were some of those discoveries?

A

Thomas Hunt. Sex-linked genes and sex linkage.

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8
Q

What is one of the model organism chosen for the Human Genome Project?

A

fruit fly, which have contributed to many important biological discoveries.

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9
Q

Describe the how we do research using different organisms? Make sure to talk about transgenic organisms.

A

First we studies, Yeast which were unicellular and were simple to understand. Then we looked at Fruit flies, which were a eukaryotes. Then we looked at mice. Here we took HELA or human immortal cell lines which are derived from tumors and injected them into mice DNA making them transgenic. Here, we took a faulty gene from humans, inserted it into mice and DNA, study what happened to the mice which would then help us predict what would happen to humans.

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10
Q

To determine principles of linkage and recombination, Thomas Hunt Morgan cross what fly with what?

A

He crossed a true-breeding fruitfly with red eyes and blue wings (pr+pr+vg+vg+) with a fly with recessive purple eyes and vestigial wings(prprvgvg).

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11
Q

What were the results of Hunt’s testcross between true-breeding and recessive flies?

A

He discoved a high number of parental phenotypes and a low number of recombinant phenotypes

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12
Q

What is a parental pehnotype?

A

Where the phenotype of the offspring looks exactly the same as one of its parents.

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13
Q

What is a recombinant phenotype?

A

When the offspring does not exhibt the same phenotype of either parent.

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14
Q

With hunt’s observation of high number of parental phenotypes and a low number of recombinant phenotypes, what did he propose?

A

That pr and vg genes are physically associated on the same chromosme and the behavior of these linked genes is due to chromosome recombination.

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15
Q

In Hunt’s experiment, what was the F1 generation show?

A

All F flys were wildtype in phenotype and were heterozygous for both pairs of alleles: pr+prvg+vg

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16
Q

Genetic recombination is what?

A

A process in which two homologous chromosomes exchange segments with each other by crossing over during Propose 1 of meiosis.

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17
Q

Genetic Recombination is a function of what?

A

of the disrance between the linked genes– the nearer two genes are, the greater chance they will be inherited together as a unit.

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18
Q

What is performed when you have an unknown phenotype of a gene to determine if it is homozygous dominant, heterozyhous, or homozygous recessive? Explain this process.

A

A test cross is performed. Here we take the unknown phenotype and cross it with a double recessive: T! x tt.

There are two possible outcomes, either you can get all dominant phenotype in which case T! is TT. Or you can get 50% dominant and 50% recessive phenotype in which case the unknown is Tt.

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19
Q

In Hunt’s experiment, what two phenotypes did he testcorss and what was its progeny?

A

Hunt crossed his F1 dihybrid with red eyes and normal wings from his initial experiment of crossing a wild type with a true recessive and a double recessive male. This was done to determine the alelle pattern of the F1 generation: T! Here the gametes from the female [derived from pr+prvg+vg] were: pr+vg+, prvg, pr+vg, prvg+, and were corssed with gamete from male parent: prvg. This produced the progeny of 1,339 pr+prvg+vg(heterozygous). 1,195(true recessive)[both parentals], 151 red vestigial, 154 purple normal both recombinants adding to 2,839 total progeny. This was different to 709 of each possible outcome expected if assorted independently.

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20
Q

In Hunt’s experiment, what caused the progeny of red eyes vestigial wings and purple eyes and normal wings recombinants?

A

Meiosis in the F1 female, with Pr+prvg+vg dihybrin parent produces 4 types of gametes. Two parental gametes, pr+vg+, and prvg resulting with no crossing over between the genes. The recombinants pr+vg anf vg+pr result from CROSSING OVER between homologous chromatids in meiosis prophase 1. Meiosis in the male testcross parent produces one type of gamete: prvg(recessive.)

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21
Q

How do you calculate recombination frequency?

A

You add the parentals and recombinants to give total progeny. Then you use the formula, # of recombinants/total progeny x100 for the percent of progeny that are recombinants (i.e recombination frequency)

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22
Q

Each pair of linked genes has a characteristic ____ ______which reflects the distance between them on their chromosome.

A

recombination frequency

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23
Q

Recombination frequncies can be used to make a ____ map.

A

Linkage map of chromosmes showing relative locations of genes.

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24
Q

A map unit is what?

A

A mu or a centimorgan (cM) is equivalent to a recombination frequency of 1%. so 10.7 % recombination frequency means there are 10.7 mu.

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25
Q

Are genes widely separated on a chromosome likely to undergo recombination?

A

genes that are widely seperated are SO likely to undergo recombination in Meisos that no linkage is detected between them– the genes assort independently.

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26
Q

Can linkage between widely seperated genes on the same chromosome still be dected?

A

Yes, by testing their linkage to one or more genes that lie between them using a linkage map.

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27
Q

What is the recombination threshold where we can’t accurately convert it to mu?

A

greater than 50%

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28
Q

Widely separated chromosomes: Genes A and B are located 57mu away from each other that cross over always happens between them, therefore linkage is not detected. However, between them, gene B is 23 mu away from A an 34 mu away from c. Are genes A and C still linked?

A

Genes A and B and B and C are close enough to show linkage which means that A and C must also be linked( on the same chromosome)

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29
Q

What does “linked” mean when talking about genes?

A

Whether 2 genes are part of the same chromosome.

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30
Q

What is the mode of inheritance?

A

indicated the patterns with which the mutant phenotype is associated.

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31
Q

What are the 6 modes of inheritance? Which 3 are most common?

A
  • Autosomal recessive, Autosomal dominant, X-linked recessive, X-linked dominant, Y-linked, mitochondrial.

The first 3 are the most common.

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32
Q

The human has 23 pairs of chromosomes. Which ones are autosomes?

A

The first 22 pairs are autosomes with the 23rd and last pair being sex chromosomes.

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33
Q

Are human traits controlled by a single gene?

A

Some human traits are controlled by a single gene which exhibit dominant and recessive inheritance patterns.

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34
Q

What analysis is used to track inheritance patterns in families?

A

pedigree analysis

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35
Q

What is the example of a dominant pedigree analysis given in the lecture?

A

Juvenile glaucoma- a disease which causes degeneration of optic nerve leading to blindness.

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36
Q

Does the dominant trait skip generations?

A

No, it appears in every generation.

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37
Q

What are some examples of dominant traits in humans

A

Middigital hair- presence of hair on middle-segment of fingers.
Brachydcatyl- short fingers
Huntington disease- degeneration of nervous system, starting in middle age
Hypercholesterolemia- most common mendilan disorder- elevated levels of blood cholesterol and risk of heart attack
polydactyly- extra fingers or toes

PTC sensitivy- PCT tastes as bitter
Camptodactyly- inabiltyt to straighten finger

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38
Q

What are some examples of recessive traits?

A

Albinism- lack of melanin pigmentation
Red-Green color blindness- inabilty to distingulish red or green wave lengths of light.
Cystic fybrosis- abnormal gland secrectoin, leading to liver degeneration and lung failure.
Duchene muscular distrophy- wasting away of muslces during childhood
Hemophillia- inabilty of blood to clot properly, some clots form but process is delayed.
Sickle cell anemia- Defective hemoglobin that causes red blood cells to curve and stick together.

Alkaptonuria- inability to metabolize homogentistic acid

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39
Q

Describe Autosomal Dominant Inheritance. Include which chromosomes, what allele combination is presented, any differences between males and females, and does it skip generations?

A

Human Autosomal traits are located on the non-sex chromosomes(1-22). Heterozygotes exhibit the affected phenotype. Males and females are equally affected and may transmit the disease. Affected phenotype does not skip a generation.

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40
Q

What does a punnet square of a autsomal dominant trait look like?

A

Affected heterzygous parent(Aa) crossed with an unaffected (aa) parent produces- 2 Aa affected heterozygote and aa unaffected homo-zygote.

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41
Q

In a pedigree, what does a unshaded square represent?

A

unaffected male

42
Q

In a pedigree what does a unshaded circle represent?

A

unaffected female

43
Q

In a pedigree, what does a shaded square represent?

A

affected male

44
Q

In a pedigree, what does a shaded circle mean?

A

affected female

45
Q

In a dominant pedigree, would the trait skip a generation?

A

No, it would be seen in every generation.

46
Q

Describe Autosomal Recessive Inheritance. Include allele charaterstics, sex-related discrepensies.

A

Heterozyotes carry the recessive allel but exhibit the wild type phenotype. Male and females are equally affected and may transmit the disease. This may skip generations.

47
Q

Can Autosomal Recessive Inheritance skip generations?

A

May skip generations.

48
Q

Describe the punnet square of a Autosomal Recessive Inheritance cross.

A

Unaffected carrier parents- heterozygous(Cc) are crossed. The make 1(25%) homozygous dominant (CC) unaffected non-carried. 2 (50%) heterozygous carrier(parental) and 1(25%) dominant recessive (cc). Genotypic ratio is 1:2:1. Phenotypic ratio is: 3:1.

49
Q

What is an example of an autosomal recessive inheritance pedigree?

A

albinism- condition in which the pigment of melanin is not produced due to nonfunctional allele of the enzyme tyrosinse. Males and females affected equally. Most affected individuals have unaffected parents.

Alss PKU- autosomal recessive

50
Q

in autosomal recessive inheritance, do most individuals have affected or unaffected parents?

A

most individuals have unaffected patterns.

51
Q

What does a half shaded box denote in a pedigree?

A

A male carrier

52
Q

What does a half shaded circle mean in a pedigree

A

female carrier

53
Q

Can males and females be affected and transmit the gene in Autosomal dominant and recissive inheritance?

A

Yes both males and females are affected and may transmit the gene equally.

54
Q

Do traits skip generations in both autosomal dominant and recessive inheritance?

A

No Traits only skip generations in autosomal recessive and never with autosomal dominant.

55
Q

In what mode of inheritance must at least one parent be affected?

A

In autosomal dominant, at least one parent must be affected. In autosomal recessive both parents can be carriers and not exhibit the trait.

56
Q

Genes located on the sex chromosomes are called?

A

Sex-linked genes which are inherited differently in males and females.

57
Q

What is the sex chromosome pair for females?

A

They have two copies of the X chromosome forming a homologous XX pair

58
Q

What is the sex chromosome pair for males?

A

Males have 1 X and 1 Y chromosome making an XY combination.

59
Q

What type of sex gamete does the homogametic sex producted.

A

Females produce only X gametes with respect to sex chromosomes.

60
Q

What type of sex gamete does the heterogametic sex produce?

A

Males produce two types: X and Y with respect to chromosomes.

61
Q

In what ways can sex chromosomes be different in species other than humans?

A

In some insects have XX females and XO males(no y). In birds, butterflies, and some reptiles, males have an homologous pair of sex chromosomes (ZZ) and females are the heterogametic sex with ZW sex chromosomes.

62
Q

Describe sex determination using X and Y chromosome. Include a punnet square.

A

Half the gametes produced by and XY male carry and X chromosome and half carry a Y.

A sperm carrying a X chromosome fertilizes an X-bearing egg cell, it produces a XX female.

A sperm carrying a Y chromosome fertilizes an X-bearing egg cell, it produces an XY male.

Using a punnet square, an XX female crossed with an XY female has 50% chance of male and 50% chance of female (1:1).

63
Q

What is sex-linkage?

A

The pattern by which different sets of alleles located on sex-chromosomes in males and females are inherited

64
Q

Describe the difference between males and females with alleles on X chromosomes?

A

These X-linked alleles occur in two copies in females(XX) but only once in males(XY).

65
Q

Do recessive X-linked traits occur more frequently in males or females?

A

Males; because males posses only a single X chromosome and therefore only require one mutated X in order to be affected whereas females need both XX chromosomes [from each parent] to be mutated in order to be affected.

Females may still have mild symptoms.

66
Q

What is the pedigree example of an X-linked recessive trait?

A

DMD- Duchenne muscular dystrophy-
An affected male with unaffected parents mean the mother is a carrier for the gene.

May skip generations.

67
Q

What are some examples of traits caused by recessive alleles on the X chromosome?

A

Red-Green color blindness, hemophilia, DMD.

68
Q

What exampled individual was affected with hemophillia?

A

Hemophillia and X-linked recessive disease affected Queen Victoria. She was an heterozugous carrier for the recessive allele (Xh+Xh). She passed the on the mutant alle but did not have symptoms of the disease.

69
Q

Describe the pedigree of a X-linked dominant trait?

A

Both males and females are equally affected.

Ex: hereditary enamel hypoplasia- X-linked dominant trait.

an XeXe unaffected female with XEy affected male producced an unaffected male XeY, affected XEXe females.

Does not skip generations

70
Q

Does X-linked dominant traits occur more in males or females?

A

With an affected male and unaffected female, female offspring always exhibit the disease because the XE affected allele is passed on from the father always and causes issues. In this case, males are not affected.

Yet, with an affected heterozygous female and unaffected male, the results are mixed: 25% chance of affected male, 25% chance of affected female, 50 affected chance of unaffected male or female(25-25).

71
Q

human sex determination depends on what gene?

A

the SRY gene on the Y chromosome

72
Q

How does the SRY gene work?

A

In Early embryonic development, structures that give rise to reproductive organs are same in XX and XY embryos. When the SRY gene on the Y chromosome becomes active, parts of these structures develops as testes.

Hormones from testes cause tissues for female structures to degenerate and tissues for male structures to develop.

73
Q

What is dosage compensation mechanism?

A

When The effects of each chromosome are equalized by inactivating one of the 2 X chromosomes in mosy body cells of females. Females have two X chromosomes. One of these is folded into a tightly coiled state aka. barr body through a condensation process packing the chromatin, similar to cell division.

74
Q

What is a barr body?

A

When one of the X chromosomes are folded and packed into a tightly coiled state in X chromosome inactivation.

75
Q

when does the random inactivation of the X chromosome happen?

A

Early in embryonic development, one of 2 XX chromosomes are RANDOMLY deactivated with that same X inactivated in all descendants of the cell.

76
Q

Describe the phenotypic effects of X chromosome inactivation.

A

If the 2 X chromosomes carry different alleles of a gene, one allele will be active in some cell lines and other will be active in others.

For some genes, X chromosome inactivation produces recognnizably different effects in distinct regions of the body(i.g. calico cats)

77
Q

Describe the example of Calico Cats in X-chromosome inactivation.

A

In Calico Cats, the O dominant gene is X-linked and is responsible for orange fur color. The X chromosome also has the o recessive gene with has no affect on fur which allows the B Autosomal gene for black fur to be displayed.

In a cell, with the X-chromosome for o recessive inactivated with chromosome inactivation, the O dominant orange fur is expressed. The black gene is not expressed in this case because of of EPISTASIS- one gene man mask the expression of another.

But in another cell, the O dominant allele on one X chromosome is inactivated, and thus the o recessive no effect on fur gene is expressed. Thus no masking of the phenotypic expression of B gene producing black fur.

This produces a mixture of orange and black fur in a calico cat. White fur is also mixed in when a different autosomal gene blocks pigment deposition completely.

78
Q

How does Xist IncRNA spread across the X chromosome?

A

A model sugests that Xist (protein) coats the X chromosome by searching in three dimensions, modifying chromosome structure and spreading to newly accessible locations(X-chromosome inactivation.

79
Q

What are chromosomal mutations?

A

changes in chromosome structure or chromosome number

80
Q

How do changes in the chromosome strucure i.e mutations occur?

A

it occurs when the DNA breaks, and the broken fragments may be lost or attach to the same or different chromosomes. These changes in chromosome number include addition or loss of one or more chromosome or entire sets of chromosomes.

81
Q

What are the 4 ways changes in chromosome structure can occur?

A
  1. deletion - a segment is lost from a chromosome
  2. duplication- a segment is broken from one chromosome and inserted into its homologu, adding to the ones already there
  3. translocation- a segment is attached to a different nonhomolohous chromosome
  4. inversion- A segment reattaches to the same chromosome but in revered orientation, order of genes is replaced.
82
Q

What is deletion?

A

A segment is lost from a chromosome.

A B C D E F G H
A B C D E G H

loss of F

83
Q

What is duplication?

A

A segment is brokem from one chromosome and inserted into its homologue, adding to the ones already there.

A B C D E F G H
A B C D E D E G H

84
Q

What is translocation?

A

A broken segment is attached to a different non-homologous chromosome

A B C D E F G H

       K   L M N

A B C D E N

      K  L M F G H
85
Q

What is inversion?

A

A segment reattaches to the same chromosome but in reverse orientation. order of genes reversed

A B C D E F G H
A B C D G F E H

86
Q

What is nondisjunction?

A

The failure of homologous pairs to seperate during the first meiotic division or of chromatids to separate during second meiotic division.

Whole, single chromosomes may be lost or gained in cell .

87
Q

What are individuals with extra or missing chromosomes called?

A

Aneuploids

88
Q

What are euploids?

A

individuals with a complete set of chromosomes

89
Q

Explain Nondisjunction in Meiosis I leading to aneuploids.

A

During the first meiotic division, nondisjuncton causes both chromosomes to be deliver to the same pole of the spindle, producing 2 gametes with an extra chromosomes and 2 with a missing ones.

90
Q

Explain nondisjunction in Meiosis II leading to aneuploids.

A

Nondisjunction during M2 produces 2 normal gametes, 1 with a missing chromosome, and 1 with an extra chromosome.

91
Q

What is general prognosis of aneuplody in humans?

A

In humans, addition or loss of an autosomal chromosome generally causes embryos to develop so abnormally that they naturally abort.

92
Q

What affects humans born with an extra copy of chromosome 21?

A

Trisomy 21 causes Down Syndrome, which is characterized by short stature and moderate to severe mental retardation.

Down syndrome arises from nondisjunction of Chromosome 21, primarily in women and increases with maternal age. Women greater than 45 have a significantly higher chance.

93
Q

In which Meiosis would there have had to be nondisjunction to produce an offspring with trisomy 21?

A

Meiosis I because that’s when nondisjunction results in 2 gametes with 3 chromosomes and 2 with only 1.

In meiosis II, 2 gametes are normal and 2 are either missing and having a chromosome.

94
Q

How does Aminocentesis relate to aneuploidy?

A

Aminocentesis is a medical procedure where we can derive fetus cells from the Amniotic fluid in the womb and establish a karyotype.

We can then look at the karyotype and determine if the child has any issues like Trisomy 21 or Klinefelter syndrome.

95
Q

What is an Alpha-fetoprotein?

A

An AFP test is performed to measure the baby’s risk of birth defects and genetic disorders including chromosomal abnormalities.

96
Q

In Aneuploidy of sex chromosomes what does nondisjunction the female XX chromosome lead to.

A

One gamete gets 2 XX chromosome and the other gets no chromosome: O

When the O gamete combined with a Y sperm, the zygote is not viable: YO

When the O gamete combined with another X sperm, it leads to turner syndrome: XO.

When the XX gamete combines with a Y Sperm, it produces klinefelter syndrome: XXY. (Inactivation leads to XY)

When XX gamete combines with X sperm, it leads to Triple X syndrome: XXX.

97
Q

In Sex chromosome nondisjunction, what does O egg Y sperm lead to?

A

OY: non viable pregnancy.

98
Q

In Sex chromosome nondisjunction, what does O egg X sperm lead to?

A

XO: turner syndrome

99
Q

In Sex chromosome nondisjunction, what does XX egg Y sperm lead to?

A

Klinefelter syndrome: XXY(inactivation leads to XY)

100
Q

In Sex chromosome nondisjunction, what does XX egg X sperm lead to?

A

Triple-X syndrome: XXX

BIOL 2311 (5 decks)

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