bio 303 exam one

chapters 1-6

Pangenesis

* Each part of the body contains genetic information for that particular part.​
* Specific particles, called gemmules, carry information from parts of the body to the reproductive organs.​
* Then passed to the embryo at the moment of conception.​

EVERYTHING RUNS TO THE GROIN (everywhere beginning hypothesis)

Inheritance of acquired characteristics

* Traits acquired in an individual’s lifetime​
* Become incorporated into hereditary information​
* Are passed on to offspring​

Giraffe example: the act of trying to get food elongated the neck through the generations ​

Preformation

* Inside the egg or sperm exists a fully formed miniature adult​
* A homunculus (the person sperm)
* Simply enlarges in the course of development​

Blending inheritance

 proposed that the traits of offspring are a blend, or mixture, of parental traits. This idea suggested that the genetic material itself blends, much as blue and yellow pigments blend to make green paint; it also suggested that after having been blended, genetic differences could not be separated in future generations​

Cell theory

* All life composed of cells​
* Cells arise only from preexisting cells​
* Cell the fundamental unit of structure and function in living organisms

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* Matthias Schleiden and Theodor Schwann

Walter Flemming

* chromosomes
* Observed the division of chromosomes in 1879​
* Published an in depth description of mitosis​

Darwin

* evolution
* evolution through natural selection

Gregor mendel

* Discovered basic principles of heredity (father of modern genetics) -- pea plants

Genome

*  is a complete set of genetic instructions for any organism.​

\-Like a blueprint​

\- either RNA or DNA

Chromosomes

highly compacted DNA

Genes

* Fundamental unit of heredity
* can come in multiple forms
* confer phenotype
* located on chromosome

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Central dogma

DNA creates RNA creates Proteins

\*\*What are some of the implications of all organisms having similar genetic systems?\*\*​

A. that all life forms are genetically related​

B. that research findings on one organism’s gene function can often be applied to other organisms​

C. that genes from one organism can often exist and thrive in another organism​

D. all of the above

D. all of the above

transmission genetics

how traits are passed on, generation to generation

* The basic principles of heredity​
* How traits are passed from one generation to the next​
* Focus is on the individual organism​

Molecular genetics

how genetic material behaves at a molecular level

* The chemical nature of the gene​
* How genetic information is encoded, replicated, and expressed​
* Focus is the gene and its structure, organization, and function​

population genetics

how genes behave in a population (many individuals)

* The genetic composition of populations​
* How genetic composition changes geographically and with the passage of time​
* Focus is the group of genes found in a population​

Model genetic organism

 organisms with characteristics that make them useful for genetic analysis.​

Common characteristics of model organisms

* Short generation time​
* Production of numerous progeny​
* The ability to carry out controlled genetic crosses​
* The ability to be reared in a laboratory environment​
* An accumulated body of knowledge about their genetic systems​

**Would the horse make a good model genetic organism? Why or why not?**​

No, horses:​

* Are expensive to house, feed, and propagate​
* Have too few progeny​
* Have a generation time that is is too long​

Weismann: germ-plasm theory​

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

Why didn’t prokaryotes evolve into eukaryotes?

“if it isn’t broke don’t fix it”. Their traits fit their niche so there was no need for them to evolve (they live and reproduce just fine as they are)

Eukaryotic cells

* has nucleus
* relatively large
* Multiple linear DNA models
* DNA is complexed with histones
* large amounts of DNA
* has membrane-bound organelles

Prokaryotic cells

* No nucleus
* relatively small
* Usually one circular DNA model
* Small amounts of DNA
* no membrane-bound organelles

Prokaryotic cell reproduction

* One circular chromosome ​
* One origin of replication (ORI) : start site of DNA replication​
* Two circles begin to peel apart as ​
* Produces two identical organisms (unless there is a mutation) ​

Diploid cells

carry two sets of genetic information (somatic cells in humans) (two chromosomes)

Haploid cells

carry one set of genetic information ( gametes in humans) (one chromosome)

Centromere

attachment point for spindle microtubules​ in chromosomes. Repetitive DNA that does not code for protein

Telomere

tips of linear chromosomes. Caps that protect chromosomes from deterioration

Kinetochore

where spindle fibers connect and pull sister chromatids apart

**What would be the result if a chromosome did not have a kinetochore?**​

* Spindle microtubules would not attach to the chromosome.​
* Some daughter cells would be missing a chromosome.​

Life cycle of a cell

* **Interphase:** an extended period between cell divisions, DNA synthesis, and chromosome replication phase​
* **M phase:** mitotic phase​
* Phase checkpoints: key transition points​

G1

growth; proteins necessary for cell division synthesized​

G1/S checkpoint

• regulated decision point​​

S

DNA synthesis

G2

biochemical preparation for cell division

G2/M checkpoint

only passed if DNA is completely replicated and undamaged​

G0 phase

stable, nondividing, period of variable length

Which is the correct order of stages in the cell cycle?​

a. G1, S, prophase, metaphase, anaphase​

b. S, G1, prophase, metaphase, anaphase​

c. prophase, S, G1, metaphase, anaphase​

d. S, G1, anaphase, prophase, metaphase​

a. G1, S, prophase, metaphase, anaphase

Mitosis

Separation of sister chromatids (somatic cells)

Prophase

chromosomes condense. Each chromosome posses two chromatids. The miotic spindle forms

Prometaphase

the nuclear membrane disintegrates. spindle microtubules attach to chromatids

metaphase

chromosomes line up on the metaphase plate

Anaphase

sister chromatids separate and move toward opposite poles

Telophase

chromosomes arrive at spindle poles. The nuclear membrane re-forms and the chromosomes relax (titty phase)

Meiosis

production of haploid gametes

Fertilization

the fusion of haploid gametes

genetic variation

the consequences of meiosis

Interphase

DNA synthesis and chromosome replication phase​

Meiosis 1

separation of homologous chromosome pairs, and reduction of the chromosome number by half​

Meiosis 2

separation of sister chromatids, also known as equational division​

Crossing over

chromosome segments from the sister chromatid of one chromosome to the sister chromatid of the other synapsed chromosome―exchange of genetic information, the first mechanism of generating genetic variation in newly formed gametes —- prophase 1 ​

Prophase one

• synapses

• tetrad

• crossing over

Tetrad

closely associated four-sister chromatids of two homologous chromosomes​

Synapsis

close pairing of homologous chromosomes​

Chiasmata

where crossing over takes place

Metaphase one

random alignment of homologous pairs of chromosomes along the metaphase plate (random alignment is another way genetic variation is formed)

Anaphase one

separation of homologous chromosome pairs, and the random distribution of chromosomes into two newly divided cells―second mechanism of generating genetic variation in the newly formed gametes​

Telophase one

cleavage forms and two new sets of genetic information are separated into two different cells (creates two non-identical cells unlike in mitosis) ​

Interkinesis

chromosomes relax before they enter meiosis two (where they recondense and go through another round of division) ​

Meiosis two

the production of 4 haploid non-identical gametes

Which event takes place in meiosis II but not in meiosis I?​

a. crossing over​

b'. contraction of chromosomes​

c. separation of homologous chromosomes​

d. separation of chromatids​

d. separation of chromatids

Shugoshin

strengthens the cohesion near centromere, and prevents sister chromatids from separating during meiosis one

Spermatogenesis

Male gamete production

Produces 4 sperm

oogenesis

female gamete production

produces one ovum (because of disintegration of second smaller gamete in each meiosis stage)

B. His study of plant chromosomes

Which of the following factors did not contribute to Mendel’s success in his study of heredity?​

1. his use of the pea plant​

2. his study of plant chromosomes​

3. his adoption of an experimental approach​

4. his use of mathematics​

​What is the difference between a locus and an allele? What is the difference between genotype and phenotype?

A locus is a place on a chromosome where genetic information encoding a characteristic is located.​

An allele is a version of a gene that encodes a specific trait.​

A genotype is the set of alleles possessed by an individual organism.​

A phenotype is the manifestation or appearance of a characteristic.​

Independent assortment

Alleles at different loci separate differently (Traits on two different chromosomes separate independently)

The traits encoded by both alleles appeared in the F2 progeny.​

How did Mendel know that each of his pea plants carried two alleles encoding a characteristic

• Both the principle of segregation and the principle of independent assortment refer to the separation of alleles in anaphase I of meiosis.​

• The principle of segregation says that these alleles separate.​

• The principle of independent assortment says that they separate independently of alleles at other loci

How are the principles of segregation and independent assortment related, and how are they different?​

d.probability that the difference between observed and expected numbers could be due to chance​

A chi-square test comparing observed and expected numbers of progeny is carried out, and the probability associated with the calculated chi-square value is 0.72. What does this probability represent?​

1. probability that the correct results were obtained​

2. probability of obtaining the observed numbers​

3. probability that the difference between observed and expected numbers is significant​

4. probability that the difference between observed and expected numbers could be due to chance​

Probability and rule

multiply the probabilities of both situations together

probability or rule

add the probabilities of the two events together

Meiosis​

  -Independent assortment​

-Crossing over​

What process causes the genetic variation seen in offspring produced by sexual reproduction?​

Hermaphroditism

both sexes in the same organism

Monoecious

both male and female reproductive structures in same organism

Dioecious

either male or female reproductive structures present in the organism

XX - XO system

• xx female

• XO male (hemigenetic)

XX-XY system

• XX female homogenetic

• XY male heterogenetic

Primary pseudo autosomal region

How do X and Y chromosomes connect?

ZZ-ZW system

• ZZ male

• ZW female

Haplodiploidy system ​

• Haploid set- male

• diploid set- female

b. Gametes of the heterogametic sex have different sex chromosomes; gametes of homogametic sex have the same sex chromosome.

How does the heterogametic sex differ from the homogametic sex?​

1. The heterogametic sex is male; the homogametic sex is female.​

2. Gametes of the heterogametic sex have different sex chromosomes; gametes of homogametic sex have the same sex chromosome.​

3. Gametes of the heterogametic sex all contain a Y chromosome.​

4. Gametes of the homogametic sex all contain an X chromosome.​

• In chromosomal sex determination ​

  -Males and females have chromosomes that are distinguishable. ​

• In genic sex determination​

  -Sex is determined by genes, but the chromosomes of males and females are indistinguishable. ​

• In environmental sex determination​

  -Sex is determined fully or in part by environmental effects.​

How do chromosomal, genic, and environmental sex-determining systems differ?​

Turner syndrome

XO; 1/3000 female births

Klinefelter syndrome

xxxy, xxy, xxxxxy or xxyy; 1/1000 male births

SRY gene

What gene on the y chromosome determines maleness

c. Poly-x male

What is the phenotype of a person who has XXXY sex chromosomes?​

1. Klinefelter syndrome​

2. Turner syndrome​

3. poly-X male​

3.X+Y

What was the genotype of the few live F1 red-eyed males obtained by Bridges when he crossed a white eyed female with a red-eyed male?​

1. X+ ​

2. XwX+Y​

3. X+Y​

4. X+X+Y​

the number of barr spots is equal to the number of x chromosomes minus one

How many Barr bodies can you expect a person to have?

complete dominance

the phenotype of the heterozygote is the same as one of the homozygotes (the normal one)

incomplete dominance

phenotype of the heterozygote is intermediate(falls within range) between the phenotypes of the two homozygotes

codominance

phenotype of the heterozygote includes the phenotype of both homozygotes

Penetrance

percentage of individuals having a particular genotype that express the expected phenotype. Proportion of individuals within a population that all have the same genotype, and express a certain phenotype

Expressivity

how intensely a phenotype is expressed

a.In incomplete dominance, the heterozygote is intermediate between the homozygotes; in incomplete penetrance, some individuals do not express the expected phenotype.

How does incomplete dominance differ from incomplete penetrance?

a.Incomplete dominance refers to alleles at the same locus; incomplete penetrance refers to alleles at different loci.

b.Incomplete dominance ranges from 0% to 50%; incomplete penetrance ranges from 51% to 99%.

c.In incomplete dominance, the heterozygote is intermediate between the homozygotes; in incomplete penetrance, heterozygotes express phenotypes of both homozygotes.

d.In incomplete dominance, the heterozygote is intermediate between the homozygotes; in incomplete penetrance, some individuals do not express the expected phenotype.

lethal allele

allele causes death at an early stage of development, so some genotypes may not appear among the progeny

b. Ww

A cross between two green corn plants yields 2/3 progeny that are green and 1/3 progeny that are yellow. What is the genotype of the green progeny?

a.WW

b.Ww

c.ww

d.W_(WW and Ww)

Multiple alleles

for a given locus more than two alleles are present within a group of individuals (ex blood type ABO)

c. 15

How many genotypes are possible at a locus with five alleles?

a.30

b.27

c.15

d.5