Bio 1510 Final Exam

Who was the first to suggest the central role of chromosomes in genetics and authored a paper announcing the rediscovery of Mendel’s work in genetics?

Carl Correns

Who hypothesized the Chromosomal theory of inheritance based on observations that similar chromosomes paired together during meiosis

Walter Sutton

The normal eye color for fruit flies is ____, the mutant eye color for fruit flies is ____

Red, white

The scientific names of the fruit flies that T.H Morgan was working with were called

Drosophila melanogaster

What eye color were all F1 progenies when T.H. Morgan crossed the two eyed flies

All were red

T.H Morgan found that the eye color gene for fruit flies resides on the ____ chromosome, because all the white eyed flies in F2 were ___

X, male

Traits (like fruit fly eye color) determined by sex chromosome genes are

sex-linked

The pair of dissimilar chromosomes that still pair during meiosis and mitosis

Sex chromosomes

Sex determination in fruit flies is based on the

number of X chromosomes

2 X chromosomes (in fruitflies) =

female

1 X and 1 Y chromosome (In fruitflies) =

male

Sex determination ____ across organisms

varies

Sex determination is based on the presence of a __________ in humans

Y Chromosome

In humans, a female has:

No Y chromosomes

In humans, a male has:

1 Y chromosome

In birds, the male has

two Z chromosomes

In birds, the female has:

Z and W chromosomes

Some insects (like grasshoppers) are either ____, (female) or _____ (males)

XX, XO

The O in male insect pairs indicates

an absence of a chromosome

In honeybees, the females are ____ and the males are _____

Diploid, haploid

Total human chromosomes

46

what are non-sex chromosomes called

autosomes

how many pairs of autosomes are in humans

22

how many pairs of sex chromosomes

1 pair

In humans the Y chromosome is

highly condensed

recessive alleles on male’s X have no __ _______ on Y

active counterpart

“Default” for humans is

Female

For humans to become males, a ____ gene on the Y chromosome is required

SRY

In organisms like humans with XY sex-determination, ___ genes from the Y chromosome are expressed

few

A single recessive sex-linked gene in XY organisms can produce

a recessive phenotype

In XY organisms, certain genetic diseases affect males to a ______ degree than females

greater degree

examples of diseases males are more prone to in XY organisms are _____, ______

Red-green color blindness, hemophilia

_______ _______ ensures the equal expression of genes from sex chromosomes even through the number is different between sexes

Dosage compensation

In mammalian somatic female cells, 1 X chromosome is randomly inactivated and is highly condensed into a ______ ______

Barr Body

Females’ heterozygous genes on the X chromosomes are ____ _____, with an example being the ______ _____

genetic mosaics, Calico cat

Two organelles other than the nucleus that contain genes

Mitochondria and Chloroplasts

Traits from Mitochondria and Chloroplasts _____ _____ _____ the chromosomal theory of inheritance

do not follow

Genes from mitochondria and chloroplasts are often passed to the offspring from only one parent, often the mother.

Maternal inheritance

In plants, chloroplasts are also often inherited from _____, but this is species dependent

the mother

in ______ _______, the phenotype exhibited by a mutant allele depends on which parent contributed the allele to the offspring

genomic imprinting

genomic imprinting of chromosome 15 in humans results in _____ if from the mother, and _____ if from the father

Angelman syndrome, Prader-Willi syndrome

igf 2 stands for

insulin-like growth factor

igf 2 encodes a growth factor critical for _____ development and growth in mice

prenatal

only paternal allele of igf 2 is expresse, which means the phenotype of heterozygotes depends on which parent contribute the _____

mutant allele

Imprinting is an example of

Epigenetics

A mitotically and/or meiotically stable change in gene function that does not involve a change in DNA sequence

Epigenetic inheritance

One mechanism of Epigenetics that involves methylation is

DNA methylation

A Second (linked to the first one) mechanism of Epigenetics that involves modification is

histone modification

A third mechanism of Epigenetics that involves RNAs is

non-coding RNA’s

A fourth mechanism of Epigenetics that involves organization is

nuclear organization

A fifth mechanism of Epigenetics that involves proteins is

Alterations to proteins involved in chromosome structure

The four mechanisms of epigenetics are

DNA methylation and histone modification, Bon-coding RNA’s, Nuclear organization, and alterations to proteins involved in chromosome structure

Early geneticists realized that they could obtain information about the _____ between genes on a chromosome, called Genetic Mapping

distance

Distance estimates based on patters of genetic ______ (crossing over) between genes

recombination

If crossover occurs, parental alleles are recombined, producing _____ _______

recombinant gametes

What was the hypothesis of the Creighton and McClintock experiment?

Crossing over involves a physical exchange of genetic material

What was the prediction of the Creighton and McClintock experiment?

Recombination of visible differences in a chromosome should correlate with genetic recombination of alleles

Creighton and McClintock tested their hypothesis using two visible chromosome markers, being a ______ extension marker and a ____ knob marker

Yellow, Green

Creighton and McClintock looked for changes in

Kernel color and texture

Creighton and McClintock found that genetically _______ progeny also have physically ______ chromosomes

recombinant, recombinant

Creighton and McClintock concluded that a ______ ________ of genetic material accompanied genetic recombination

physical exchange

________ is the basis for genetic maps

recombination

An undergraduate in T.H. Morgan’s lab that put Morgan’s observation that recombinant progeny reflected relevant location of genes in quantitative terms

Alfred Sturtevant

As the physical distance on a chromosome ________, so does the_______ of recombination occurring between the gene loci

increases, probability

Each increase/decrease of a 1% chance of recombination as you move along the length of a chromosome is equal to

map unit (m.u.)

1 map unit is equal to

1 centimorgan (cM)

Perform a testcross with doubly heterozygous individuals then count progeny to to _______ cM

calculate

If a testcross reveals that 180 offspring have a specific trait out of 1000, what is the cM between the loci?

18 cM (180/1000 = 18% = 18 cM)

If homologous pairs undergo two crossovers between loci, then the _______ _______ is restored (goes back to how it was)

parental combination

Multiple crossovers lead to an _______ of the true genetic distance

estimate

Odd numbers of crossover events produce

recombinant gametes

No crossover OR even numbers of crossovers produce

paternal gametes

The relationship between true distance and recombination frequency is _________

not linear

Uses three loci instead of two to construct maps

Three-point testcross

The _________ allows tracking of recombination events on either side in a three-point testcross

Middle gene

In any three-point cross, the class of offspring with two crossovers is the ______ class

least frequent

In practice, geneticists use three-point crosses to determine the ______ of genes, then use data from the closest two-point crosses to determine ______

order, distances

Some human traits are controlled by a single gene and some of these exhibit dominant and recessive _______

inheritance

__________ is used to track inheritance patterns in families

Pedigree analysis

Dominant pedigree example

juvenile glaucoma

Recessive pedigree example

albinism

Juvenile glaucoma causes degeneration of optic nerve leading to _______, and the dominant trait appears in every generation

blindness

Albinism is a condition in which the pigment ______ is not produced

melanin

Form of albinism due to a nonfunctional allele of the enzyme _____

tyrosinase

Albinism effects males and females ______ and most affected individuals have _______ parents

Equally, unaffected

________ is a disease that affects a single protein in a cascade involved in formation of blood clots

Hemophilia

Form of hemophilia is caused by an X-linked recessive allele which means that heterozygous females are ______ carriers

asymptomatic

A single amino acid change in a single protein can result in __________, for example, __________

clinical syndrome, Sickle cell anemia

Sickle cell anemia is the first human disease shown to be the result of a mutation in _________

a protein

Sickle cell anemia is caused by a defect in the oxygen carrier molecule, ________, and leads to impaired ________ delivery to tissues

hemoglobin, oxygen

_________ for sickle cell allele exhibit intermittent illness and reduced life span

Homozygotes

________ for sickle cell allele appear normal

Heterozygotes

Heterozygotes for sickle cell allele do have hemoglobin but with __________

reduced ability

Sickle cell allele is particularly prevalent in people of __________, where the proportion of heterozygotes higher than expected

African descent

The higher proportion of heterozygotes in Africa is due to sickle cell’s resistance to ________

malaria

_________ is the failure of homologues or sister chromatids to separate properly during meiosis, changing the number of chromosomes (usually lethal)

Nondisjunction

gain or loss of a chromosome, the result of nondisjunction

Aneuploidy

Loss of a chromosome

Monosomy

Gain of a chromosome

Trisomy

Human embryos trisomic for five of the _______ autosomes can survive birth, being autosomes 13, 15, 18, 21 and 22

smallest