Genetics Exam 1

Definitions of Genomics, Proteomics, and Bioinformatics

1. Genomics - Study of genomes, studies structure/function/evolution of genes 2. Proteomics - Identifies set of proteins present in a cell under set conditions and studies their functions/interactions 3. Bioinformatics - Develops hard/software for processing nucleotide/protein data

What is a genotype and a phenotype?

1. Genotype - The genetic makeup 2. Phenotype - Expressed and observable features

Homologous chromosomes vs Sister chromatids

1. HC - Chromosomes that are similar in respect to their genetic loci and centromere placement (Present in reproductive division) 2. SC - Identical copies (present in cell division)

What is a haploid and diploid number and what are some examples?

1. Haploid (n) - A cell or organism that has a single set of unpaired chromosomes (ex. gametes - eggs/sperm) 2. Diploid (2n) - A cell or organism containing two complete sets of chromosomes 1 from each parent. (ex. normal somatic cells)

What is the theory of chromosomal inheritance and who created it?

1. Inherited traits by genes on chromosomes transmitted through gametes 2. Gregor Mendel

Who is Gregor Mendel and why did he get lucky with picking garden peas as his model organism?

1. Father of genetics 2. Only 2 alleles possible for each trait and he took detailed notes

What are 3 kinds of mutations?

1. Loss-of-function mutation - Mutation causes gene change in confirmation enzyme, thus, change in affinity. If loss is complete it is known as a Null allele 2. Gain-of-function mutation - Some mutations enhance function of wild-type allele function. Often dominant allele 3. Neutral mutation - Gene product does not present a phenotypic change

What is it called when the centromere is attached at different parts of the sister chromatids/homologous pairs?

1. Middle - Metacentric 2. Lower - Submetacentric 3. Even lower - Acrocentric 4. End - Telocentric

What theory did Charles Darwin propose and did anyone else come up with this idea?

1. Natural selection - Descent with modification (evolution). Through evolution, the best traits for the environment that something lives in has a higher chance of survival leading to the "better" genes being passed on to the next generations 2. Yes, Alfred Wallace

What are some important genes on the Y chromosome?

1. PAR - Pseudo autosomal region (Shares homology with part of X chromosome. Allows it to attach/detach with X chromosome during meiosis) 2. SRY - Sex-determining region Y. Triggers testes formation (Lack of this region will produce a female. Absent in X chromosome) 3. MSY - Male-specific region of the Y (Mostly unique section to Y chromosomes. Does have a few similarities to X)

Difference between a eukaryote and a prokaryote

1. Prokaryotes do not contain a nuclei 2. They are smaller in size 3. They do not have membrane bound organelles 4. Circular chromosomes

A couple each with blood type AB and normal pigmentation have a child with AB blood type and albinism. What is the probability that their next child will have the same phenotype as the first child?

1/8

With incomplete dominance, a likely ratio resulting from a monohybrid cross would be ________.

1:2:1

What are the 3 cases in sex-determining temperatures for some organisms?

Case I: Low temp -> females and high temp -> males Case II: Opposite case I (low temp -> males, high temp -> females) Case III: Low and high temps -> females and intermediate temps -> males

What happens in Interphase?

Check if cell is ready to divide, time of growth, chromosomes duplication. Broken into 3 stages (G1, S, G2)

Genetic information contained in DNA that encodes for an amino acid is referred to as a(n) ________.

Codon

Individuals from two separate true-breeding strains of white deer mice are crossed yielding all grey offspring. White is recessive to gray color based on crossing mice from each strain with a grey mouse. Which of the following would best explain this result?

Complementation

What conditions are likely to apply if the progeny from the cross AaBb× AaBbappear in the 9:3:3:1 ratio?

Complete dominance, independent assortment, and no gene interaction

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________.

Genes found on the Y chromosome

The presence of more than two alternative forms of a given gene would be called ________.

Multiple alleles

Assuming independent assortment, what proportion of the offspring of the cross AaBbCcDd × AabbCCddwill have the aabbccddgenotype?

0

Turner Syndrome Characteristics

1. 45, X (Female) 2. Has female genitalia and internal ducts but ovaries are rudimentary. Short, skin flaps on neck, underdeveloped breasts, broad shield like chest, normal intelligence

Triplo-X Syndrome Characteristics

1. 47, XXX 2. Women often normal. Do not realize have syndrome until learn infertile. Underdeveloped secondary sex characteristics, sterile, intellectual disability does occur

Klinefelter Syndrome Characteristics

1. 47, XXY (Male) 2. Tall with long arms and legs, large hands and feet, testes rudimentary, infertile, slight breast enlargement, rounded hips

Jacob's Syndrome Characteristics

1. 47, XYY 2. Over 6ft tall, subnormal intelligence, many have personality disorders/more aggressive

What is the theory of spontaneous generation and who disproved it?

1. Creation of living things from non-living components 2. Louis Pasteur

What are the nitrogenous bases and which do they bond to?

1. DNA - A=T (Adenine and Thymine) and G=C (Guanine and Cytosine) 2. RNA - A=U (Adenine and Uracil) Note: Adenine and guanine are Purines and thymine and cytosine are Pyrimidines

What is DNA and RNA made of and what is the difference between the two?

1. DNA - Nitrogenous base, deoxyribose sugar (5 carbon based), phosphate 2. RNA - Nitrogenous base (1 different from DNA), ribosomal sugar, phosphate

Disjunction vs Nondisjunction

1. Disjunction - Separation of chromosomes during anaphase stage of cell division 2. Nondisjunction - Failure to separate chromosomes during the anaphase stage of cell division. Leads to monosomy/trisomy

What is epistasis? Give an example

1. Expression of 1 gene or gene pair masks/modifies effect of another gene pair. (can be dominant or recessive) 2a. Bombay Phenotype (blood type). Even though child has an A, B, or AB blood type, it will appear to be an O because it lacks a completely formed H substance and cannot make A/B antigens 2b. Labrador Retriever Coat colors: BB=Black, bb=brown. Recessive epistasis of the ee gene. Ee and EE allows for black or brown coat but ee=lacks melanin disposition=yellow lab (BBee=yellow, Bbee=yellow, BbEe=black)

What are the stages of Mitosis and what happens in each?

1. Prophase (46 chromos) - Chromosomes shorten/coil. Copies connect at centromere of chromos, centrosomes (made of 2 centrioles) move to opposite ends of cell, nuclear envelope degrades 2a. Prometaphase (46 chromos) - Period of chromosomal placement because of the spindle fibers attached at the kinetochore 2b. Metaphase - Configuration down the metaphase plate. Other protein enzymes break down sister chromatid connection except for centromere (separase=enzyme and centromere protected by shugoshin) 3. Anaphase (92 chromos) - Shugoshin completely breaks down and sister chromatids separate/pulled to opposite ends of the cell 4a. Telophase (92 chromos) - Nuclear envelopes develop, chromosomes uncoil, spindle fibers revert 4b. Cytokinesis (46 chromos per cell) - Complete cytoplasmic separation leads to 2 whole cells

Who created the cell theory and what is it?

1. Schleiden and Swann (1830s) 2. All organisms composed of basic structural units called cells, which derive from pre-existing cells

What is the endosymbiotic theory and why do people believe it?

1. Theory that mitochondria and chloroplasts were previously independent bacteria but made a deal with eukaryotic cells to become apart of each other 2. Both mito and chloro have their own unique DNA that is circular and resembles bacteria

Triploid vs Trisomy

1. Triploid (3n) - Contains an extra set of chromosomes (69 chromosomes per cell) 2. Trisomy - Contains an extra chromosome on a specific pair (47 chromosomes per cell)

What is a lethal allele?

1. Usually causes death before an individual can reproduce and/or results in spontaneous abortion or miscarriages 2. Can be dominant or recessive

What is codominance? Provide an example

1. When both alleles are dominant and are equally expressed. 2. AB blood type and MN glycoprotein blood groups

What is incomplete dominance? Provide an example

1. When neither allele is dominant. Results in an intermediate/blended phenotype. 2. Cross between a plant with red flowers and one with white flowers produces pink offspring

Who created the theory of epigenesis and what is it?

1. William Harvey 2. Believed organisms develops from fertile egg by succession of events that will transform the egg to an adult

What is the difference between x-linked inheritance, sex-limited inheritance, and sex-influenced inheritance?

1. X-linked - Allele only found on X chromosomes. Can be dominant or recessive. When dom, will lead to both sexes having the trait (Rett syndrome: Males die in-utero), when recessive, males show trait more often because of the XY (they are hemizygotes) (color-blindness) 2. Sex-limited - Traits only expressed in one sex and not the other 3. Sex-influenced - Traits that are only expressed when under the influence of certain hormones. These traits can be observed in both sexes. (ex. Male pattern baldness)

Drosophila Melanogaster and sex determining ratios

1.5 - Metafemale 1.0 - Female .67-.75 - Intersex .50 - Male .33 - Metamale

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene. Two parents with normal pigmentation have an albino child. What is the probability that their next two children will be albino?

1/16

A deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD) is inherited as an X-linked recessive trait in humans. A phenotypically normal woman (whose father had G6PD) is married to a man with normal G6PD function. What fraction of their sons would be expected to have G6PD deficiency?

1/2

In the mouse, gene B can produce black pigment from a colorless precursor molecule. A mouse having at least one B allele can produce black pigment, whereas the homozygous recessive mouse (bb) cannot and is albino. The agouti locus (A) can convert the black pigment to brown in the presence of at least one dominant A allele, whereas the homozygous recessive (aa) cannot convert the black pigment to brown. What would be the probability of an albino mouse offspring if the parents were genotypes AaBb and AAbb?

1/2

The white-eye gene in Drosophilais recessive and sex-linked. Assume that a white-eyed female is mated to a wild-type male. What would be the phenotypes of the offspring?

1/2 wild-type females and 1/2 white-eyed males

The sex of birds, some insects, and other organisms is determined by a ZWchromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XYin humans). Assume that a recessive lethal allele on the Zchromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female?

2:1 male to female

A couple in which one parent is blood type A and the other is blood type B, and both have normal pigmentation, have a child that is blood type O and has albinism. What is the probability that their next child will have normal pigmentation and blood type A?

3/16

Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what phenotypic ratio is expected if the F1s are crossed?

3:1

How many genotypes and phenotypes exist for blood type?

6 genotypes and 4 phenotypes

How many different possible gametes can be obtained from an organism with the following genotype AaBbCc?

8

What is an allele?

An alternative version of a gene (Gregor Mendel's unit factor )

What factor of life leads to a higher chance of nondisjunction?

Age - mostly eggs have an issue with age because they are premade in the womb and are exposed to radiation and other such things throughout life (ex. The older the mom -> increased chance of down syndrome)

Which of the following statements would be the most likely scenario of offspring ofa woman exhibiting an X-linked recessive disorder and a man that does not exhibit the trait?

All daughters will not have the disorder and all sons will have the disorder

Mendel indicated that traits were made up of unit factors. Today, we call unit factors ________.

Alleles

What are autosomes?

Any chromosome that is not a sex chromosome

Centromere

Area where the chromatids of a chromosome are attached

Which protein is responsible for converting androgens (testosterone) into estrogens?

Aromatase

What is a karyotype?

Arrangement of chromosomes according to length/centromere position (except 21 and 22)

Autosomal dominant vs autosomal recessive

Autosomal dominant - Individual only needs one copy of the mutated gene to express the trait (Huntington's disorder) Autosomal recessive - Individual needs both copies of the mutated gene to express the trait (Tay sach's disease)

What is paired to each Carbon in DNA? (GUESSED)

C1 - Nitrogenous base C2 - Hydrogen? C3 - Phosphate C4 - Oxygen? C5 - Phosphate

If a scientist changed a cell's ionic composition and complementarity between DNA strands could no longer occur, what would the scientist first detect?

DNA becomes single stranded

Dominant vs Recessive

Dominant - When allele is present, this trait will be expressed Recessive - Allele is least likely to be expressed unless both alleles are recessive which leads to an expression

What is a synapse in meiosis?

Each bivalent leads to one unit tetrad (2 pairs of chromosomes, 4 chromatids)

Why do chromosomes need to be tightly coiled?

Easier to move them around

What is pleiotropy?

Expression of a single gene has multiple phenotypic effects

What do G1, S, and G2 do?

G1 - Initiates new cell cycle, decides if enough room, nutrients, etc... for growth S - Synthesis and duplication of DNA G2 - Sends to mitosis after checks. Note: If a cell does not pass the checkpoints, it will be sent to G0 (nondividing but metabolically active). Either issue fixed goes into mitosis or never replicates

When you cross an F1 generation (heterozygous x heterozygous), what are the phenotypic and genotypic ratios shown?

Genotype - 1:2:1 (Homo dom, hetero, homo recess) Phenotype - 3:1

Genetics is defined as the branch of biology associated with ________.

Heredity and variation

What is segregation?

How pairs of gene variants are separated into reproductive cells (development of haploid gametes)

What is a Barr Body?

Inactive X chromosome. Body wants to have equivalent to one X in genes. (Barr bodies do not stop all genes on the X chromosomes or it does not occur until later stages of fetal development hence why XXX, XXY, etc... show different or odd traits)

At which stage of cell division do sister chromatids go to opposite poles?

Mitosis anaphase and Anaphase II of Meiosis

Which of the following has one Barr body?

Klinefelter's and normal female

Organisms that are well understood from a scientific standpoint and are often used in basic biological research are often called ________.

Model organisms (Fruit flies, mice, pea plant, E. coli, etc)

What kinds of experiments did Gregor Mendel perform?

Monohybrid and dihybrid crosses

What are the steps of Meiosis and what happens in each?

Meiosis I: 1. Prophase I - Duplicate genetic material. Homologous pairs match up and perform crossing-over (swap genetic material). Centromeres move to opposite sides of cell, nuclear envelop breaks down. Note: Bivalent: Each matched pair homologous chromos or 4 chromatids) 2. Metaphase I - Chromosomes max short/coiled, tetrad bind to spindle fibers and move to the metaphase plate. Alignment of tetrads is random (random assortment) 3. Anaphase I - Homologous chromosomes separate leading to disjunction. Half a tetrad (4 chromatids) leads to a dyad (2 chromatids). Randomly pulled to opposite poles. (Separation of homologous chromosomes) 4a. Telophase I - Reappearance of nuclear membrane around dyads. Nucleus enters short interphase period but do not replicate. 4b. Cytokinesis again Meiosis II: Like mitosis 1. Pro II - Each dyad (sister chromatid) attached at centromere 2. Meta II - Centromeres positioned at meaphase plate by spindle fibers 3. Ana II - Spindle fibers pull centromeres apart leading to 1 chromatid per side of cell (separation of sister chromatids) 4a. Telo II - 1 member homolog chromosomes (now monads) at each pole 4b. Cytokinesis again. In total, 4 haploid gametes - 4 sperm or 1 viable egg and 3 polar bodies

For an individual with the XXY chromosomal composition, the expected number of Barr bodies in interphase cells is ________.

One

When you cross individuals and get a 1:1 ratio in flowers, (half white, half purple) what kind of genotypes were the parents?

One parent was heterozygous while the other was homozygous recessive

What is heredity?

Passing on of physical or mental characteristics genetically from one generation to another.

What is complementation????

Phenomenon by which the effects of two different nonallelic mutations in a gene are partly or entirely canceled out when they occur together? (Ex. If there is a mutation in homologous chromosomes in gene A at the beginning of one homologous chromosome then a mutation on the end of gene A on other homologous chromosome = No complementation BUT if there is a mutation on the first homologous chromosome in gene A and in the second homologous chromosome in gene B then complementation can occur)

Once a protein is made, its biochemical or structural properties play a role in producing ________.

Phenotype

What other theory does the theory of epigenesis go against?

Preformationism- Fertile egg contains entire mini adult called a homunculus

What did James Watson and Francis Crick do?

Proposed the double helix model of DNA

What is a kinetochore?

Protein structure on chromatids where the spindle fibers (microtubules) attach (muffin top)

Chiasma

Region chromatids intertwined/connected

A primary discovery to generate recombinant DNA molecules was the use of ________.

Restriction enzymes

The nucleolus organizer region (NOR) is responsible for production of what type of cell structure?

Ribosomes

Which of the following is true about the second meiotic division?

Sister chromatids disjoin and are pulled to opposite poles

What is a somatic cell?

Soma = body - Any cell not pertaining to reproduction

What were the 7 traits Mendel studied in pea plants?

Stem height Seed shape and color Pod shape and color Flower and position

What are the ends of a chromosomes called?

Telomeres

Which of the following processes describes the formation of a complementary RNA molecule?

Transcription

If you get a ratio of 9:3:3:1 when you self-cross individuals, what were the parents?

They were heterozygous dihybrids

Assume that you are told that a particular organism, Drosophila, has the XO chromosome complement. You are also told that the autosomal complement is a normal 2n. You know that in humans the XO complement is female determining. What would be the sex of this fly and why?

This fly would be male due to an X:A ratio of 1/2.

What is a self-cross?

This is a cross between siblings

What does vg+/vg+ mean for a fruit fly?

This is a homozygous dominant allele for wild-type wings (normal)

What are mutations?

Variations in genes -> alleles, the process produces an alteration in DNA or chromosome structure (Changes in genetic material)

Mendel crossed two pea plants with round seeds. All seeds of the offspring were round. He then crossed a plant with round seeds to a plant with wrinkled seeds and all offspring had wrinkled seeds. Which is dominant?

Wrinkled is dominant

In Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of ________.

X chromosomes

With which of the following would hemizygosity most likely be associated?

X-linked inheritance

What is Xic and Xist responsible for?

Xic (X-inactivation center) - Genetic expression only shown on the X chromosome that is inactivated Xist (X-inactive specific transcript) - Large RNA product and does not encode protein and is not translated. Covers X gene to aid in inactivation

Which gene is dependent on the X:A ratio for it's function in sex determination in Drosophila?

sxl