Exam 1: Gen Bio Review

Question 1

Describe a chromosome, its anatomy, and its various forms

Answer 1

-A chromosome consisting of just one chromatid is a monad. If it has two chromatids, it is a dyad.

-A chromosome is made of chromatin fibers that coil and condense

-Chromosomes are visible only during mitosis and meiosis but are always present

-Electron microscopy of chromosomes in varying states of coiling led to the folded-fiber model

Question 2

Compare and contrast the similarities and differences between homologous chromosomes and sister chromatids.

Answer 2

Homologous chromosomes: Homologous chromosomes contain identical gene sites along their length. Each site is called a locus. (2n) They pair up during meiosis.

Sister chromatids: The sister chromatids are joined to each other via the centromere and only become separated when cell division occurs. They are identical and are created through synthesis and separated during anaphase of mitosis and anaphase 2 of meiosis.

Question 3

Contrast Complete, Incomplete, and Co- Dominance

Answer 3

Codominance: Joint expression of both alleles in a heterozygote

Complete Dominance: Dominant allele completely expressed.

Incomplete Dominance: Intermediate phenotype. This allelic relationship led to the incorrect concept of blending inheritance.

Question 4

Gene

Answer 4

An inherited factor (encoded in the DNA) that helps determine a characteristic

Question 5

Allele

Answer 5

One of two or more variations of a gene

Question 6

Locus

Answer 6

Specific place on a chromosome occupied by an allele

Question 7

Genotype

Answer 7

Set of alleles possessed by an individual organism

Question 8

Phenotype or trait

Answer 8

An appearance of manifestation of a characteristic

Ex: Blue eyes

Question 9

Characteristics or character

Answer 9

An attribute or feature

Ex: Eye color

Question 10

Centrosome

Answer 10

An organelle near the nucleus of a cell which contains the centrioles from which the spindle fibers develop in cell division.

Question 11

Centrioles

Answer 11

-They occur in pairs perpendicular to each other
-9 triplets of microtubule arrangements
-Nontubulin proteins hold them together

Question 12

Nucleolus

Answer 12

An amorphous component of the nucleus where ribosomal RNA (rRNA) is synthesized and where the initial stages of ribosomal assembly occur

Question 13

Nucleoid

Answer 13

The nucleoid is an irregularly shaped region that houses genetic material. This is only found in prokaryotes.

Question 14

Diploid vs haploid

Answer 14

Haploid cells are those that have only a single set of chromosomes while diploid cells have two sets of chromosomes.

Question 15

Centromere

Answer 15

The contricted region of the chromosome to which kinetochores form and microtubules attach.

Question 16

Eukaryotic cell characteristics

Answer 16

-Polysaccharide cell walls
-Methionine
-Linear chromosomes, rarely plasmids
-80S Ribosomes

Question 17

Draw metacentric, submetracentric, acrocentric, and telocentric chromosomes and be able to identify where the centromere is

Answer 17

1) Middle

2) Between middle and end

3) Close to end

4) End

Question 18

What is the function of the telomeres?

Answer 18

They protect the ends of chromosomes

Question 19

Pseudohomologues

Answer 19

Behave as homologs in meiosis

Ex: X and Y

Question 20

Describe the characteristics of a model organism.

Answer 20

-easy to grow
-cheap
-observable characteristics with two distinct forms
-high brood size
-easy to selectively breed
-single season maturation time
-true-breeding strains
-precendence
-other research showed that pea hybrids could be produced

Question 21

Describe the experimental details that contributed to Mendel’s success.

Answer 21

-good choice of a model organism
-simple experimental design
-good quantitative records
-seven visible features with two contrasting traits

Question 22

Relate Mendel’s first three postulates to the results of a monohybrid cross.

Answer 22

1) Unit factors exist in pairs

2) Dominance/recessiveness of those pairs

3) Segregation of the alleles of a single gene

Question 23

Relate Mendel’s forth postulate to the results of a dihybrid cross.

Answer 23

4) Independent assortment

Unit factors that determine different traits assort independently during gamete formation

All possible gamete combinations form with equal frequency.

Question 24

Relate the rediscovery of Mendel’s work with the Chromosomal Theory of Inheritance.

Answer 24

-Genetic material in living organisms is contained in chromosomes

– Separation of chromosomes during meiosis served as basis for Mendel’s principles of segregation and independent assortment

Mendelian Genetics coupled with
Chromosomal Theory of Inheritance provides the basic principles of gene transmission

1. Genes are present on homologous
   chromosomes
2. Chromosomes segregate. Therefore the alleles of genes present on chromosomes segregate
3. Chromosomes assort independently. Transmission of alleles at one gene locus does not
   influence the transmission of other gene loci.

Question 25

Describe the stages involved in mitosis

Answer 25

Prophase: -Nuclear envelope breaks down -Chromosomes condense and become visible -Centrioles divide, move, establish poles Prometaphase: -Spindle fibers form -Centrioles reach opposite poles -Equatorial plane referred to as metaphase plate -Period of chromosome movement to equatorial plane of cell -Chromosomes are clearly double structures Metaphase: -Chromosome configuration following migration -Centromeres align on metaphase plate Anaphase: -Sister chromatids separate into individual chromosomes and migrate to opposite poles Telophase -Cytokinesis -Uncoiling of the chromosomes -Re-formation of the nuclear envelope – Spindle fibers disappear – Nuclear envelope reforms

Question 26

List the cell cycle checkpoints and describe what is being “checked” at each.

Answer 26

G1/S -Monitors size cell has achieved -Monitors condition G2/M -Monitors if DNA replication is complete -Monitors damaged DNA M (metaphase) Monitors successful formation of spindle fiber system and attachment to kinetochores

Question 27

List the major proteins involved in organizing and partitioning DNA throughout mitosis.

Answer 27

Kinetochore -Multilayered protein plates associated with centromere – Spindle fibers (microtubules) bind to kinetochore; chromosomes migrate Cohesin: -Protein complex that holds sister chromatids together Shugoshin: -Protein that protects cohesin from being degraded by separase at the centromere Separase: -Enzyme that degrades cohesin

Question 28

Karyokinesis

Answer 28

Genetic material partitioned to daughter cells during nuclear division

Question 29

Interphase

Answer 29

G1 S: DNA is synthesized G2 G0: Point in G1 phase where cells are nondividing, but a metabolically active state

Question 30

Nucleosome

Answer 30

The individual, beadlike histone DNA complexes that make up the subunits of chromatin

Question 31

Differentiate between the terms dyad and diploid.

Answer 31

A chromosome consisting of just one chromatid is a monad. If it has two chromatids, it is a dyad. Haploid cells are those that have only a single set of chromosomes while diploid cells have two sets of chromosomes

Question 32

Describe the aspects of meiosis that contribute to genetic variation in sexually reproducing species.

Answer 32

Crossing over, independent assortment, and segregation

Question 33

Describe the Chromosomal Theory of Inheritance.

Answer 33

Genes are found on chromosomes

Question 34

Explain the relationship between meiosis and Mendel’s principles of inheritance.

Answer 34

Mendel’s principle of segregation can be explained by the homologous pairing and segregation of chromosomes during meiosis Mendel’s principle of independent assortment can be explained by the relative behavior of (nonhomologous) chromosomes during meiosis

Question 35

Truebreeding

Answer 35

A kind of breeding wherein the parents would produce offspring that would carry the same phenotype if mated to itself.

Question 36

Describe sex-influenced and sex-limited traits

Answer 36

Sex-influenced: dominant for males, recessive for females Sex-limited: only one organism expresses the phenotype

Question 37

Gene linkage

Answer 37

Two gene loci in close proximity will tend to be inherited together

Question 38

Incomplete penetrance

Answer 38

A trait may not be visible despite having the determinant genotype

Question 39

Imprinting

Answer 39

The influence an allele has over a trait may change.

Question 40

Wild-type (wt) allele

Answer 40

Occurs most frequently in nature and is usually, but not always, dominant

Question 41

Loss-of-function mutations

Answer 41

Hypomorphic- partial loss Null- complete loss

Question 42

Tay Sachs Disease

Answer 42

autosomal recessive on the physiological level and codominant on the molecular level

Question 43

Reasons for mitosis

Answer 43

Growth Development (zygote) Cell division

Question 44

What is one way you could distinguish prophase from pro metaphase?

Answer 44

Spindle fiber attachment appears in pro metaphase

Question 45

Dihybrid is synonymous with

Answer 45

heterozygous

Question 46

Can a crossover cause a dyad chromosome to have non-identical sister chromatids?

Answer 46

Yes

Question 47

Does the Chromosomal Theory of Inheritance state that DNA is the inherited material passing from one generation to the next?

Answer 47

No

Question 48

What has both DNA and protein binding functionality?

Answer 48

Kinetochores

Question 49

When would you expect to find bipolar spindle fiber attachment?

Answer 49

Metaphase of mitosis and meiosis 2

Question 50

If there is a 1/2 chance of a child inheriting one syndrome and a 1/2 chance of the same child inheriting another syndrome, what is the probability that they will inherit either syndrome?

Answer 50

3/4 1/2+1/2 - (1/2*1/2) = 3/4