Exam 1

Assume that long earlobes in humans are an autosomal dominant trait that exhibits 30% penetrance. A person who is heterozygous for long earlobes mates with a person who is homozygous for normal earlobes. What is the probability that their first child will have long earlobes?

.15

In a hypothetical mouse species, brown fur (B) is completely dominant to white fur (b), and long fur (L) is completely dominant to short fur (l). If two mice heterozygous for both traits mate and produce a litter of pups, what is the probability that an individual pup will have white, short fur?

1/16

A fruit fly has 4 pairs of chromosomes, whereas the house fly has 6 pairs of chromosomes. How many different combinations are possible in the gametes of fruit flies?

16

In pea plants, plant height is controlled by a single autosomal dominant gene. Tall plants (H) are dominant to short plants (h). In a cross of two heterozygous tall plants, which phenotypic ratio is expected in the resulting offspring?

3:1

What is the end result of meiosis?

4 gametes

Suppose Jonathan breeds flowers and wants to optimize the production of offspring with both short stems and white flowers, which are coded for by two genes with the recessive alleles t and p, respectively. In flowers T codes for tall stems and P codes for purple flowers. Jonathan crosses two heterozygotes that produce 656 offspring. How many of these 656 offspring are expected to have both short stems and white flowers?

41

A fruit fly has 4 pairs of chromosomes, whereas the house fly has 6 pairs of chromosomes. How many different combinations are possible in the gametes of house flies?

64

What is a gene?

A small section of functional DNA

locus

A specific place along the length of a chromosome where a given gene is located.

Cell theory began to develop in 1839, following the research of Matthias Schleiden and Theodor Schwann into plant and animal tissues. Both the botanist Schleiden and the physiologist Schwann noticed that every organism they viewed under a microscope, whether plant or animal, was composed of cells. Their observations that all living species are made up of one or more cells led to the early formation of cell theory. Which tenet of cell theory is described by the paragraph about the historical observations of cells?

All organisms are composed of one or more cells

A cell has a circular chromosome and histone proteins associated with its DNA, but lacks a nuclear membrane. What domain does this cell belong to?

Archaea

What do prokaryotes and eukaryotes have in common?

Both contain DNA and use ribosomes to synthesize proteins.

quantitative characteristics

Characteristics that vary along a continuum, usually due to influence of two or more genes.

dihybrid crosses

Cross or mating between organisms involving two pairs of contrasting traits

Color blindness is a sex linked recessive trait. A female is colorblind in one eye, and not both. Explain why this can happen.

Different X chromosomes are being silenced

what types of cell is categorized by it's nuclear membrane surrounding the DNA of the cell?

Eukaryotes

Which idea of Mendel requires at least 2 genes to be demonstrated?

Genes assort independently in diploids

A fruit fly has 4 pairs of chromosomes, whereas the house fly has 6 pairs of chromosomes. Based on chromosome number, in which species would you expect to more genetic variation among the progeny?

House fly

secondary oocytes

One of the products of meiosis I in female animals; receives most of the cytoplasm.

first polar body

One of the products of meiosis I in oogenesis; contains half the chromosomes but little of the cytoplasm.

Model Genetic Organisms

Organisms with characteristics that make them useful for genetic analysis

What happens during anaphase 2 of meiosis?

Sister chromatids separate from each other and migrate to opposite ends of the cell.

spermatogonia

The diploid cells in a testis that can give rise to primary spermatocytes.

How is a true breeding yellow-seeded pea plant different from a hybrid yellow-seeded pea plant?

They have the same phenotypes but different genotypes

XX-XO sex determination

This is seen in some insects. In this system females are XX and males are XO; there is no O chromosome the O just mean there is no additional chromosome.

what pattern of inheritance does color blindness follow?

X-linked recessive

Is it possible for a man to have different color-blindness phenotypes in each eye?

Yes, in an XXY male with a different active X in each eye.

The Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two sons who die of bleeding after circumcision (removal of the foreskin from the penis), any additional sons that she has should not be circumcised. The bleeding is most likely due to the X‑linked disorder hemophilia. Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should be. Is this religious law consistent with sound genetic principles?

Yes, the woman is a carrier and half of her sons will be affected. Her sisters may also be carriers, but her brothers sons will get their X chromosomes from their mothers, who are unlikely to be carriers of the allele.

Autosome

a chromosome that does not determine sex

genomic imprinting

a phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent

Crossing over

a process in which homologous chromosomes exchange genetic information. generates genetic variety

Suppose there is a vial containing a single generation of flies from a cross. There is an interesting phenotype where many individuals have abnormally long hairlike bristles, sensory organs extending from the dorsal thorax, as opposed to the short wirelike wild‑type bristles among the other siblings. References state that this mutant has a dominant mutation called Suave (Su) and that the phenotype of flies that are heterozygous or homozygous for Su appear phenotypically identical. Which fly should be crossed to a Suave male from this vial in order to generate progeny that help determine the male's genotype?

a wild type female sibling

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. a. What is the probability that a sperm from the father will contain the PKU allele? b. What is the probability that an egg from the mother will contain the PKU allele? c. What is the probability that their next child will have PKU? d. What is the probability that their next child will be heterozygous for the PKU allele?

a. 1/2 b. 1/2 c. 1/4 d. 1/2

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. a. What are the phenotypic ratios in the F2? b. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring? c. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

a. 9/16 bitter fruits, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots; 1/16 sweet fruit, no spots b. All bitter fruit with yellow spots c.1/4 bitter fruits, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots

In cats, curled ears result from an allele, Cu, that is dominant over an allele, cu, for normal ears. Black color results from an independently assorting allele, G, that is dominant over an allele for gray, g. A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. What phenotypes and proportions are expected from the two crosses? a. Two of the F1 cats mate b. An F1 cat mates with a stray cat that is gray and possesses normal ears

a. 9/16 black cats, curled ears; 3/16 black cats, normal ears; 3/16 gray cats, curled ears, 1/16 gray cats normal ears b. 1/4 black cats, curled ears; 1/4 black cats, normal ears; 1/4 gray cats, curled ears; 1/4 gray cats, normal ears

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albinism (a). For this question, assume it is a single gene with two alleles. If both parents display the albino phenotype, what possible phenotypes may be observed in their offspring?

albinism only

homologous pair

alike in structure and size and each carries genetic information for the same set of hereditary characteristics

cell theory

all life is composed of cells, cells only arise from preexisting cells, and the fundamental unit of structure and function in living organisms is the cell.

checkpoints

allow or prohibit a cell's progression to the next stage of mitosis

Allele

alternate forms of the same gene

Define Barr body

an inactive x chromosome

lethal allele

causes death at an early stage of development, causes some genotypes to not appear among progeny. can alter genotypic ratio of progeny. 2:1 is almost always produced by recessive lethal allele

What are the functions of mitotic cell division?

cell regeneration, asexual reproduction, and growth of multicellular organisms

haploid

cells containing a single set of chromosomes

germ-plasm theory

cells in the reproductive organs carry a complete set of genetic information that is passed to the egg and sperm

telophase

cells start pulling apart

diploid

cells that carry two sets of genetic info

polyploid

cells that contain more than two sets of genetic information

oogonia

cells that produce primary oocytes by mitotic division

cytoplasmic inheritance

characteristics are encoded by genes located in cytoplasm, always maternally passed down, never inherited from father.

polygenic characteristics

characteristics encoded by genes at many loci

continuous characteristics

characteristics that exhibit a continuous distribution of phenotypes: many possible phenotypes

discontinuous characteristics

characteristics that have a few easily distinguished phenotypes

Suppose a man is heterozygous for heterochromia, an autosomal dominant disorder which causes two different colored eyes in an individual, produced 25 offspring with his normal-eyed wife. Of their children 16 were heterochromatic and 9 were normal. Calculate the chi square value for this observation.

chi square= 1.96

What are the sturctures in a cell that group genes together, are composed of chromatin (DNA and protein) and become visible under the light of a microscope during mitosis?

chromosomes

telophase 1

chromosomes arrive at the spindle poles and the cytoplasm divides

telophase 2

chromosomes arrive at the spindle poles and the cytoplasm divides

prophase

chromosomes become visible under a light microscope, spindles move to chromosomes

Prophase 1 of meiosis

chromosomes form homologous pairs and crossing over takes place

prophase 2

chromosomes recondense

Molecular genetics

concerns the chemical nature of the gene itself: how genetic information is encoded, replicated, and expressed

anaphase

connection between sister chromatids breaks down and they separate. Chromosomes move towards opposite ends of the cell

multifactorial characteristics

continuous characteristics that are both polygenic and influenced by environmental factors

backcross

cross between an f1 and a p

monohybrid cross

crosses between parents that differed in a single characteristic

cytokinesis

cytoplasmic division

expressivity

degree to which a trait is expressed

G2/M checkpoint

detection of DNA damage after replication

sex-influenced characteristics

determined by autosomal genes and inherited according to Mendel's principles, but are expressed differently in males and females.

primary spermatocyte

diploid cell that has gone through meiosis 1 and entered prophase 1

primary oocyte

diploid cells that complete meiosis 1 and divide to produce secondary oocytes

microsporocytes

diploid reproductive cells ( male, plants)

megasporocytes

diploid sex cells (female, plants)

prometaphase

disintegration of the nuclear membrane begins thisphase. Spindle microtubules enter nuclear region, each chromosome becomes attached to microtubules from opposite poles of the spindle

In Drosophila melanogaster, the level of expression of genes on the X chromosome in males is doubled. What phenomenon is this an example of?

dosage compensation

The principle of segregation

each individual diploid organism possesses two alleles for any particular characteristic, one from the maternal parent and one from the paternal parent. these alleles segregate when gametes are formed, one allele going into each gamete

epistasis

effect of a gene interaction in which one gene masks the effect of another gene at a different locus

sex-limited characteristics

encoded by autosomal genes that are expressed in only one sex

Transmission genetics

encompasses the basic principles of heredity and how traits are passed on from one generation to the next.

Spindle assembly checkpoint

ensures that each chromosome is attached to spindle fibers from opposite poles

phenocopy

environmental factors produce a phenotype that is the same as the phenotype produced by a genotype

Population genetics

explores the genetic composition of groups of individuals of the same species and how that composition changes over time and space.

XX-XY sex determination system

females are xx, males are xy

turner syndrome

females who have underdeveloped secondary sex characteristics. XO chromosomes

interphase

first stage of the cell cycle, in which the cell grows, develops and functions

microspores

four haploid cells produced by microsporocytes undergoing meiosis

spermatids

four haploid cells that are formed when a diploid reproductive cell divides meiotically

megaspores

four haploid cells, produced by megasporocytes undergoing meiosis

incomplete penetrance

genotype does not always produce expected phenotype

genic sex determination

genotypes at one or more loci determine the sex of an individual

Cohesin

holds sister chromatids together

anaphase 1

homologous chromosomes separate and are pulled to opposite poles

metaphase 1

homologous pairs of chromosomes line up in the middle

metaphase 2

individual chromosomes line up in the middle

preformationism

inside the egg or sperm there exists a fully formed miniature adult, a homunculus, which simply enlarges in the course of development

anaphase 2

kinetochores of sister chromatids separate and chromatids are pulled to opposite sides

Chromosome

long dna molecules visible during mitosis; large genetic element that carries genes essential to cellular function

G1/S checkpoint

maintains cell until necessary enzymes for replication are synthesized

zz-zw sex determination

males are zz, females are zw (sneks, butterflies, some amphibians)

dosage compensation

mechanisms that equalize the amount of protein produced by single X and two autosomes in heterogametic sex.

M phase

mitotic phase. the period of active cell division

Telomeres

natural ends or tips of a linear chromosome

Pleitropy

one gene affects multiple characteristics

testcross

one individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question

penetrance

percentage of individuals with a particular genotype that express the expected phenotype

interkinesis

period between meiosis one and two

incomplete dominance

phenotype of a heterozygous individual falls somewhere between the dominant and recessive phenotypes.

codominance

phenotype of heterozygote is not intermediate between the phenotypes of homozygotes, but rather simultaneously expresses teh phenotypes of BOTH homozygotes

genetic maternal effect

phenotype of offspring is determined by the genotype of the mother.

oogenesis

production of gametes in female organisms

spermatogenesis

production of sperm

What type of cell is categorized by its size (less than 10 um in size) and the fact that it lacks a true cytoskeleton?

prokaryote

blending inheritance

proposed that offspring are a blend of parental traits, suggests that the genetic material itself blends.

histones

protein molecules around which DNA is tightly coiled in chromatin present in eukarya and archaea

Common characteristics of model organisms

short generation time, production of numerous progeny, and the ability to be reared in a laboratory environment.

Origins of replication

sites where DNA synthesis begins; not easily observed by microscopy

second polar body

smaller cell, incapable of being fertilized

principle of independent assortment

states that alleles at different loci separate independently of one another

addition rule

states that the probability of any one of two or more mutually exclusive events is calculated by adding the probabilities of these events. Either or

multiplication rule

states that the probability of two or more independent events taking place together is calculated by multiplying their independent probabilities. And rule

Pangenesis

suggested that specific pieces of information travel from various parts of the body to reproductive organs, from which they are passed to the embryo

chi square test

sum of (observed-expected)^2/expected, tells how likely it is that results happened because of coincidence and not a miscalculation

What common features must all genomes have, no matter where they exist?

the ability to store the entire set of information the organism needs for reproduction and development, and the ability to replicate the genetic information accurately for the next generation.

ovum

the cell that received most cytoplasm that is now an egg

Metaphase

the chromosomes arrange in the middle

mitosis

the process of nuclear division

How does the structure of DNA encode genetic information?

the sequence of bases

What is the product of mitosis?

two cells genetically identical to the original cell

secondary spermatocyte

two haploid cells yielded from meiotic division of primary spermatocytes

Sister chromatids

two identical copies of a chromosome held together at a centromere

Synapse

very close pairing association

concept of dominance

when two different alleles are present in a genotype, only the trait encoded by one of them (the dominant allele) is observed in the phenotype

Lyon Hypothesis

within each female cell one of the two x chromosomes is inactivated, which is random