Biology 181 Terms For Final Test

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Nonsister chromatids recombine genes.

Exchange of genetic material between nonsister chromatids of a bivalent.

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meisosis.

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Crossing over

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Zygote = recombined chromosomes from parents

Fusion of gametes = _____________

During _____________ parental genes are combined(22^3)^2 combinations =
70,368,744,000,000

Advantage = variability in genes increases chance for survival

The union of haploid gametes to produce a diploid zygote.

(2) The addition of mineral nutrients to the soil.

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Fertilization

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Offspring have different combination of chromosomes & genes than parents.

Crossing-Over
Independent Assortment
Fertilization

Generic term for the production of offspring with combinations of traits that differ from those found in either parent.

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Genetic recombination

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bivalents = paired chromosomes that code for the same traits

1 inherited from each parent
same length, same banding pattern

genes may code for different variations of same trait

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One of these is inherited from the organisms father and the other from mother. Could be called...

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Homologous chromosome, Homologous pair, Homologs

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Chromosome separation is random.

Homologous chromosomes separate ___________ & randomly.

When homologues or bivalents align at cell equator, maternal or paternal homologue may be oriented toward either pole


Result = several (2^3=8) possible chromosome combinations
22^3 = 8,388,608 combinations in humans.

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Independent assortment

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All reproductive events between one generation to the next.

Meiosis occurs only during gamete production in animals.

Spermatogenesis (males)
production of sperm
occurs in testes.

Oogenesis (females)
production of egg cell
occurs in ovaries.

The generation-to-generation sequence of stages in the reproductive history of an organism.

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Life cycle

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Prophase I
Nuclear envelope & nucleolus disappear

2 homologous chromosomes pair during ________ to form bivalents

Crossing over can occur

Meiosis I = 1st cell division
Chromosomes (DNA) duplicate

Homologues align & form ________ = bivalent or tetrad

Homologues separate

The pairing and physical connection of replicated homologous chromosomes during prophase I or meiosis.

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Synapsis

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Homologues align & form synapsis = bivalent or _____

When homologues or ________ align at cell equator, maternal or paternal homologue may be oriented toward either pole

A pair of homologous chromosomes which have joined together (are synapsed) during prophase I and metaphase I of meiosis.

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Tetrad-bivalent

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Sexual reproduction = fusion of 2 gametes (n + n) forms a diploid (2n) organism

Recombined chromosomes from parents

Fungi & algae: gametes (n) fuse to form ______ (2n), which undergoes meiosis to form haploid (n) adult.

The diploid product of the union of haploid gametes during fertilization; a fertalized egg.

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Zygote

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A descrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses).

Most traits determined by pair of _ _ _ _ _ = sections of DNA

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Gene

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Alternate forms of a gene that code for the same trait.

Any of the alternative versions of a gene that produce distinguishable phenotypic effects.

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Allele

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This masks the expression of the a specific allele.

An allele that is fully expressed in the phenotype of a heterozygote.

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Dominance

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This allele masks the expression of the __________ allele.

An allele whose phenotypic effect is not observred in a heterozygote.

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Recessive

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Alleles occur on homologous pair of chromosomes at a specific location of this

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

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Locus

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Identical alleles

Having 2 identical alleles for given gene.

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Homozygous

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Hybrid of different alleles.

Having 2 different alleles for a given gene.

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Heterozygous

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Refers to the genetic makeup (alleles) of an individual.

The genetic makeup, or set of genes and their iteractions.

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Genotype

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Refers to the physical appearance of the individual.

The physical and physicalogical traits of an organism, which are determined by its genetic makeup.

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Phenotype

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Controlled by this trait (several forms).

ABO blood types

The chance that 2 or more independent events will occur together = the product (multiplication) of their chance of occurring separately

1/2 x 1/2 = 1/4

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Multiple allelic trait

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Each dominant allele has a quantitative or ______ ______ on phenotype

The chance that an event, which can happen in 2 or more independent ways, will occur = the sum (addition) of the individual chances.

1/4 + 1/4 + 1/4 = 3/4 or 75%

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Additive effect

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Black coat color is dominant to brown in mice (B,b)
Another gene determines whether or not pigment is deposited in the hair C,c
Individuals with cc as their genotype will be albino regardless of the genotype at the coat color gene.

Affects skin, hair & eyes and is considered a pleiotropy = 1 gene affects many traits.

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Albinism

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Non-sex chromosomes.

A chromosome that is not directly involved in determining sex, not a sex chromosome.

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Autosomes

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XX = female (1X = inactive ____ ____)

Klinefelter (XXY)

Affects 1:2000
Sterile

Undeveloped testes

Some breast development

Possible retardation

____ ____ is present.

A dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome.

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Barr body

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Heterozygous individuals who are unaffected by a disorder, but who can pass disorder onto child.

Do NOT show trait, but can pass it on.

In genetics, an individual who is heterozygous at a given genetic locus, with one normal allele and one recessive allele. The heterozygote is phenotypically dominant for the characterdetermined by the gene but can pass on the recessive allele to offspring.

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Carriers

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More than 1 allele is fully expressed.

ABO blood type = multiple allelic traits.

Alleles are equally expressed.

The situations in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.

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Codominance

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Human X-Linked Disorder

8% of Caucasian men & 0.5% of women are this

Color vision receptors in the retina include 3 different classes of cone cells.

Blue-sensitive = autosomal
Red-sensitive = X chromosome
Green-sensitive proteins = X chromosome.

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Color blindness

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Occurs when 1 trait is governed by 2 or more sets of alleles

Each dominant allele has a quantitative (additive) effect on phenotype

Result = continuous range of phenotypes
height
skin color (genes code for pigment)

Polygenic Disorders:
Cleft lip
Diabetes
Schizophrenia
Allergies
Cancer

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Continuous traits

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2-trait ________ cross = cross between parents that have 2 different traits (height & color)

An organism that is heterozygous with respect to 2 genes of interest. All the offspring from the cross between parents doubly homozygous for different alleles are ________. For example, parents of genotypes AABB and aabb produce a ________ of genotype AaBb.

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Dihybrid cross

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A ________ _____ is a trait which doesn't have a range of phenotypes. For example, tongue rolling is a ________ _____ as an individual can either roll their tongue or not roll their tongue. There is no phenotype between these two phenotypes.

Determine which characteristic is dominant & code alleles accordingly

Determine genotype & gametes for both parents

Each gamete has 50% chance of receiving either allele

Example:
In humans, freckles (F) are dominant over no freckles (f). A man heterozygous for freckles reproduces with a woman without freckles. What is the probability that their child will have freckles?

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Discrete traits

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When 1 gene affects the expression of another gene
Albinism
Black coat color is dominant to brown in mice (B,b)
Another gene determines whether or not pigment is deposited in the hair C,c
Individuals with cc as their genotype will be albino regardless of the genotype at the coat color gene.

A gene at 1 locus interferes with the expression of a gene at a different locus (albinos)

Human skin color = polygenic inheritance

A type of gene interactions in which one gene alters the phenotypic effects of another gene that is independently inherited.

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Epistasis

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Phenotype of offspring = blend of 2 parental phenotypes

Red & white --> pink petals

Curly & straight hair --> wavy hair

Pitch of male voice
Lowest = PP
Baritone = Pp
Highest = pp

When an intermediate phenotype is expressed
Flower color in the carnation
Sickle cell

The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.

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Incomplete dominance

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(2n - 1) = when an individual has only 1 of a particular type of chromosome

Referring to a cell that only has one copy of a particular chromosome instead of two.

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Monosomy or Monosomic

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In genetics, the presence in an individual of two or more cell lines that are karyotypically or genotypically distinct and are derived from a single zygote.

A condition in which tissues of genetically different types occur in the same organism.

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Mosiac

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Failure of chromosomes to separate (anaphase II)

chromosomes fail to separate during oogenesis or spermatogenesis

Inherit too many or too few X or Y chromosomes

Down Syndrome: Trisomy of Chromosome 21 3 copies of chromosome 21
______________ during egg & sperm formation

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Nondisjunction

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Autosomal Dominant ________

Autosomal Recessive ________

X-Linked Recessive ________

A diagram of a family tree showing the occurance of heritable characters in parents and offspring over multiple generations.

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Pedigree

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1 gene affects many traits

Albinism = skin, hair & eyes

Sickle-cell disease
1:400 African Americans

RBC = sickle-shaped
Defect in hemoglobin
Clog vessels
Poor circulation & anemia
Resistance to malaria (1:10 = heterozygous)

A gene that affects more than 1 characteristic of an individual.

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Pleiotropy

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Occurs when 1 trait is governed by 2 or more sets of alleles

Each dominant allele has a quantitative (additive) effect on phenotype

Result = continuous range of phenotypes
height
skin color (genes code for pigment)

Disorders Associated:
Cleft lip
Diabetes
Schizophrenia
Allergies
Cancer

Epistasis = A gene at 1 locus interferes with the expression of a gene at a different locus (albinos)
Human skin color = This

An additive effect of two or more genes on a single phenotypic character.

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Polygenic inheritance

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Have more than 2n number of chromosomes

Can be lethal in animals

A chromosome alterations in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division.

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Polyploidy

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determine the sex of an individual
XX = female (1X = inactive Barr body)
XY = male (Y chromosome determines gender)

A chromosome responsible for determining the sex of an individual.

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Sex chromosomes

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Enzyme coding for black fur = active at low temperatures

Black fur only occurs on extremities (ears, nose, feet, tail)

Environment and Phenotype

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Siamese cats

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1:400 African Americans

RBC = sickle-shaped
Defect in hemoglobin
Clog vessels
Poor circulation & anemia
Resistance to malaria (1:10 = heterozygous)

Incomplete dominance = when an intermediate phenotype is expressed
Flower color in the carnation
This particular disorder

A human genetic disorder caused by a recessive allele that results in the substitution of a single amino acid in a globin polypeptide that is part of the hemoglobin protein; characterized by deformed red blood cells (due to protein aggregation) that can lead to numerous symptoms.

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Sickle cell disease

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Lysosome storage disorder
Affects 1:3,600 Jewish people (Ashkenazi)
Lack enzyme needed to digest glycosphingolipids
Symptoms:
Blindness, seizures & paralysis
Death by age 3 or 4
Carriers (Tt) = more resistant to Tuberculosis

Autosomal Recessive Disorder

A human genetic disease that caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth, followed by death within a few years.

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Tay sachs disease

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Breeding an organism of unknown genotype with ahomozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.

Used to determine if individual with dominant phenotype is homozygous dominant or heterozygous for a trait

____ individual is crossed with pure recessive individual.

This is used to ____ _____ the ressesive genetics.

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Test cross

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Human X-Linked Disorders

Color blindness
Hemophilia
Muscular dystrophy
Werewolf Syndrome
Fragile X Syndrome

X-linked (sex-linked) = genes carried on X chromosome

Y chromosome = missing these alleles.

Y chromosome cannot offset the inheritance of an X-linked recessive allele.

X inactivation and this...

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Tortoise shell cat

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(2n + 1) = individual has 3 copies of a chromosome

Down Syndrome: _______ 21

3 copies of chromosome 21
nondisjunction during egg & sperm formation

Sperm has extra chromosome 21 (23% of cases)

Translocation between chromosome 21 & 14 (5% of cases)

Gart gene causes mental retardation

Detected by: amniocentesis, chorionic-villi sampling, & karyotyping

Mothers 40+ years = at higher risk

Referring to a diploid cell that has 3 copies of a particular chromosome instead of the normal 2.

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Trisomy