USF genetics exam 1 El rady

Law of Segregation

During gamete formation, the alleles for each gene segregate from each other, so that each gamete carries only one allele for each gene.

hereditary

Passing of traits from parents to offspring

genes

DNA segments that serve as the key functional units in hereditary transmission.

the study of genetics is important for two main reasons:

1 it unifies the study of biology

2 it has profound impact on human affairs

when was the domestication of animals

13,000BC

When was the cultivation of plants

8,000BC

which philosophers provided the first formal explanations of hereditary and variation

Greek philosophers

Hippocrates

Democritus

Plato

Aristotle

Hippocrates statement on genetics

Of the semen, however, I assert that it is secreted by the whole body healthy by healthy parts, sick by sick parts. Hence as a rule, bald-headed begets bald-headed, blue-eyed beget blue-eyed."

Democritus statement on genetics

"More people become able by exercise than by their natural predisposition."

Plato statement on genetics

Advocated the selection of spouses to produce children who will develop into bodily and ethically eminent personalities

Aristotle statement on genetics

Developed a comprehensive theory of inheritance:

The male semen was only formed from the blood

It provides a "form"

The menstrual blood contains the "matter" for offspring The "form" controls and shapes the "matter" into the mature offspring

after the Greek philosophers when did the next ideas of genetics get presented

not until the 17th century

William henry presentation of genetics

Proposed that all living things originate from an egg

Introduced the Theory of Epigenesis All parts of the embryo are present potentially in the egg

The organism evolves by gradual building up and aggregation of these parts

Theory of Epigenesis

structures such as body organs are not initially present in the early embryo and are formed later

Antonie van Leeuwenhoek (1632-1723)

Discovered spermatozoa

Speculated that the sperm provides the essential life-giving properties, and the egg merely furnishes the proper environment for the embryo's nutrition and development

Theory of Preformationism

The organism is contained in one of the sex cells as a fully developed (albeit miniature) homunculus

With proper nourishment the homunculus unfolds into its adult proportions

The Spermists believed the homunculus was found in the sperm

The Ovists believed the homunculus resided in the egg

Caspar Wolff

Discredited the Theory of Preformationism

Jean Baptiste de Lamarck (1809)

proposed first theory of evolution

theory of inheritance of acquired characteristics

discredited theory of evolutionary change proposing that changes that occur during the lifetime of an individual, through use or disuse, can be passed on to the next generation

theory destroyed by Darwin

Provisional Hypothesis of Pangenesis

Cells of the developing organism are capable

of producing gemmules, which are exact but

minute copies of each body part. These are carried by the blood to the reproductive organs where they are assembled into gametes. With fertilization, the combined gemmules then separate out to different parts of the body during development.

August Weismann

disproved Darwin's pangenesis

What did August Weismann propose

The Germplasm theory of hereditary

The Germplasm theory of hereditary

Multicellular living organisms are made up of two types of tissue

Somatoplasm-body tissue essential for function of organism

Germplasm- hereditary material set aside for reproductive purposes

there was continuity of germplasm between generations, and it was associated with the nucleus

Who were the 2 most important plant hybridists before Mendel

Joseph Kolreuter

Karl Gaertner

recorded similar work did not realize significance

Johann Gregor Mendel (1822-1884)

priest who worked with garden peas in his garden used results to propose The Particulate Theory of Inheritance

Gregor Mendel's work

Was rediscovered by Hugo de Vries, Carl Correns, and Erich von Tschermak in 1900

William Bateson (1861-1926)

First to demonstrate experimentally the extension of Mendel's Laws to animals

Coined the term genetics to describe the science of heredity

Eugenics

Coined by Francis Galton

It refers to the improvement of a population by selecting its best specimen for breeding

Galton believed that many human traits are inherited and thus subjects to selection

Positive eugenics (Galton)

Encouraging the reproduction of those with beneficial traits

Negative eugenics (Galton)

Discouraging the reproduction of those with undesirable traits

The Eugenics movement had a strong impact on US public policy in the early 20th century

1. Compulsory sterilization of "eugenically-unfit" individuals 2. Laws invalidating marriages between "eugenically-unfit" individuals 3. Immigration Restriction Act

End of the Eugenics movement in the United States

In the 30s it floundered people made prejudiced experiments

Modern Eugenics

prenatal diagnosis, artificial insemination, cloning

Blending theory of genetics

Factors that control hereditary are malleable they can blend together generation after generation

what organism did Gregor Mendel decide to work with

Pisum sativum

cross-fertlization

pollen and egg are derived from different plants

self-fertilization

pollen and egg are derived from the same plant

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

P generation

Parental generation, the first two individuals that mate in a genetic cross

F1 generation (first filial generation)

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation (second filial generation)

offspring of the F1 generation

third filial generation (F3 generation)

The third generation, produced by crossing F2 organisms.

alleles

Different forms of a gene

Homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

Punnet Square Method

a method of predicting the genotypes and phenotypes of offspring in genetic crosses

law of independent assortment

the law that states that genes separate independently of one another in meiosis

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

If the genes do assort independently, what will the expected phenotypic outcome be

9:3:3:1

loss of function alleles

an allele of a gene that encodes an RNA or protein that is nonfunctional or compromised in function

commonly inherited in a recessive manner

trihybrid cross

a cross involving three traits

forked-line method

a method to solve independent assortment problems in which lines are drawn to connect particular genotypes

product rule of probability

The chance of two or more independent events occurring together is the product of their chance of occurring separately

sum rule of probability

When two events A and B are mutually exclusive the probability that A or B will occur is the sum of the probability.

binomial expansion equation

The probability of the occurrence of unordered mutually exclusive events is defined by the binomial theorem

binomial expansion equation formula

Chi-square test

a statistical test used to determine the probability of obtaining observed proportions by chance, under a specific hypothesis

chi squared formula

pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

autosomal dominant trait (1-3)

1 trait is usually present in every generation

2 Members of both sexes affected equally

3 unaffected parents produce unaffected offspring

autosomal dominant trait (4-6)

4 two affected parents can produce unaffected offspring

5 on average half the children of an affect parent will be affected

6 The homozygote for the disease-causing allele is generally, more severely affected than the heterozygote

autosomal dominant disorders

Huntington's disease, achondroplasia

polydactyly

brachydactyly

syndactyly

helio-Opthalmic outburst syndrome

Huntington's Disease (HD)

The major symptom of the disease is the degeneration of certain types of neurons in the brain

leads to personality changes, dementia, and earl death

what causes huntingtins disease

Result of a mutation in the gene that encodes a protein termed Huntington. The mutation adds a polyglutamine tract to the protein which causes aggregation of the protein in the neurons

autosomal dominant traits

freckles

widows peak

cleft chin

three explanations for autosomal dominant disorders

Haploinsufficiency

gain-of-function mutation

dominant negative mutations

Haploinsufficiency

The heterozygote has 50% of the normal protein

This is not sufficient for a normal phenotype

gain of function mutation

mutation changes protein so it gains a new function

dominant negative mutations

The altered gene product acts antagonistically to the normal product

autosomal recessive traits (1-3)

1 traits tend to skip generations

2 members of both sexes affected equally

3 unaffected parents can have an affected child

autosomal recessive traits (4-5)

4 two affected parents cannot have an unaffected child

5 Traits are more likely to occur in consanguineous marriages

autosomal recessive disorders explanation

disorders that involve defective enzymes typically have an autosomal recessive mode of inheritance

The heterozygote has 50% of the normal enzyme this is sufficient for a normal phenotype

examples of autosomal recessive disorders

cystic fibrosis, sickle cell anemia

albinism PKU and TSD

albinism

Absence of pigment in the skin, hair, and eyes

cystic fibrosis (CF)

inherited disorder of exocrine glands resulting in thick mucinous secretions in the respiratory tract that do not drain normally

Tay-Sachs Disease TSD

a fatal genetic disorder in which harmful quantities of a fatty substance buildup in tissues and nerve cells in the brain

patients die usually at 4

X-linked recessive traits (1-3)

1 Traits may skip generations

2 Most affected individuals are male

3 Affected males result from affected mothers or mothers who are carriers

X-Linked recessive traits (4-6)

4 Affected females come from affected fathers and affected or carrier mothers

5 affected females will have affected sons

6 the trait can never be transmitted directly from father to son

X-linked recessive disorders

Hemophilia

Hemophilia

An X-linked recessive disorder in which blood fails to clot properly, leading to excessive bleeding if injured.

X-linked dominant traits (1-3)

1 Trait does not skip generations

2 Affected males must come from affected mothers

3 Affected females come from affected mothers or fathers

X-Linked dominant traits (4-7)

4 Affected males have no normal daughters and no affected sons

5 Affected heterozygous females transmit the trait to approximately half of their children of either sex

6 Affected homozygous females transmit the trait to all their children

7 males are often more severely affected

X-linked dominant disorders

Vitamin D resistant rickets, Rett syndrome, Aicardi syndrome, Incontinentia pigmenti, faulty tooth enamel

Vitamin D resistant rickets

Rickets is a disorder involving softening and weakening of the bones of children primarily caused by lack of vitamin D

Y-linked traits

1. Trait only affects males

2. Affected males get it from their fathers and give it to their sons

incomplete penetrance

In the case of dominant traits, this pattern occurs when a dominant phenotype is not expressed even though an individual carries a dominant allele.

Incomplete dominance

This pattern occurs when the heterozygote has a phenotype that is an intermediate between either corresponding homozygote for example a cross between red and white equal pink

Overdominance (heterozygote advantage)

The pattern occurs when the heterozygote has a trait that confers a greater level of reproductive success than either homozygote

codominance

This pattern occurs when the heterozygote expresses both alleles simultaneously without forming an intermediate phenotype for example with human blood types an individual carry A and B with have an AB blood type

X-Linked

This pattern involved the inheritance of genes that are located on the X chromosome. In mammals and fruit flies males have one copy of x-linked genes where females have two copies

sex influenced

This pattern refers to the effect of sex on the phenotype of the individual some alleles are recessive in one sex and dominant in the opposite sex

sex-limited

In this pattern a trait occurs in only one of the two sexes. an example is breast development in mammals

lethal alleles

A lethal allele is one that has the potential of causing the death of an organism

Mutant alleles

alleles that have been altered by mutation

wildtype allele

most frequent allele associated with the common phenotype

genetic polymorphism

The existence of two or more distinct alleles at a given locus in a population's gene pool.

haploinsufficiency

The appearance of a mutant phenotype in an individual cell or organism that is heterozygous for a normally recessive trait

Expressivity

the degree to which a trait is expressed. For example, flowers with deep red color have a high expressivity of the red allele.