Biology exam 2 (Ch 8-

Compare parent offspring relationship in asexual reproduction

produces offspring that are all genetic copies of the parent and identical to each other

Compare parent offspring relationship in sexual reproduction

creates a variety of offspring (mix and match)

Explain how daughter prokaryotic chromosomes are separated from each other during binary fission

1. the cell replicates its chromosome

2. the copies move apart and the plasma membrane pinches

3. more cell wall is made, which eventually divides the parent cell into 2 daughter cells

Describe the structure of prokaryotic chromosomes

Describe the structure of eukaryotic chromosomes

Describe the phases of the cell cycle

2 Major phases

1. Interphase (Includes G1,S,G2 phases)

2. Mitotic phase (mitosis and cytokinesis)

List the stages of mitosis

Prophase, Prometaphase, Metaphase, Anaphase, Telophase, and Cytokinesis (Plants)

Events and Characteristics of Prophase

1. mitotic spindle forms (Centrosomes and fibers)

2. Centrosome encloses 2 centrioles

3. Chromatin fibers begin coiling up to form condensed chromosomes

Events and Characteristics of prometaphase

1. Nuclear envelope breaks down

2. spindle fibers attach to kinetochores anchoring sister chromatids to poles

3. chromosomes move toward the center of the cell

Events and Characteristics of metaphase

1. Chromosomes move to the cell equator and create metaphase plate

2. two sister chromatids are attached to opposite sides of the cell

Events and characteristics of anaphase

1. Centromeres of each chromosome separate into two

2. sister chromatids are now individual chromosomes

3. spindle fibers pull the chromosome along, towards opposite poles

Events and Characteristics of telophase

1. chromosomes decondense making chromatin

2. nuclei reform

3. spindle disappears

4. two genetically identical nuclei have been produced

Events and characteristics of cytokinesis (animals)

1. divides the cytoplasm into 2 daughter cells via a cleavage furrow

events and characteristics of cytokinesis (plants)

1. division of the cytoplasm into 2 daughter cells via a cell plate

How does cell density control cell division?

Density dependent inhibition stops cells from dividing once cells bump into other cells.

How do chemical growth factors control cell division?

• Most animal cells divide when stimulated by growth factors

• a set of proteins within the cell controls the cell cycle

• signals affecting critical checkpoints in the cell cycle determine whether cells grown or divide

• binding of growth factors to specific receptors on the plasma membrane is necessary for cell division

Explain how cancerous cells are different than healthy cells

• Cancer cells are a result of chromosome breakage and errors in DNA synthesis that can lead to mutations

• mutations cause cancer cells to divide uncontrollably

• cell cycle control system breaks down

• cells lose specific function of normal cells

• Cancer cells divide to form tumors (radiation and chemo interfere with cancer cell division)

Explain how chromosomes are paired

• Somatic cells contain a specific number of chromosomes according to the species

• humans have 46, 23 pairs of homologous chromosomes

• the chromosomes of a homologous pair carry genes for the same characteristics at the same place (Locus)

• Males have one pair that is not full homologous (XY)

Somatic cells

body cells

Gametes

• eggs and sperm

• haploid cells with a single set of chromosomes

Diploid

cells that have two sets of homologous chromosomes

Haploid

Cells with a single set of chromosomes

Why does sexual reproduction require meiosis?

Meiosis reduces the chromosome number from a diploid to a haploid to make gametes (eggs or sperm)

Mitosis

• begins w/ diploid parent cells that have DNA duplicated during the previous interphase

• produces 2 genetically identical diploid somatic daughter cells

meiosis

• Begins w/ diploid parent cells that have DNA duplicated during the previous interphase

• produces 4 genetically unique haploid gametes

meiosis 1

separates each homologous pair and produces two daughter cells, reduces the number of chromosomes (Diploid to haploid)

meiosis 2

• in each of the cells the sister chromatids of each chromosome separate and results in 4 haploid cells

Stages of meiosis

1. prophase 1= homologous chromosomes pair and exchange corresponding segments (Crossing over)

2. Metaphase 1= Homologous chromosomes align

3. Anaphase 1= Homologous chromosomes separate

4. Telophase 1= Nuclear membranes reform

Meiosis 2 stages

1. Prophase 2= spindle fibers attach to sister chromatids

2. metaphase 2= the chromosomes align on the equator

3. anaphase 2= sister chromatids separate

4. telophase 2= nuclear membranes reform followed by cytokinesis

How is genetic variation is produced in sexually reproducing organisms?

random fertilization of eggs by sperm greatly increases genetic variation

Define true breeding organisms

• Organisms that can transmit certain traits to all their offspring

• pass down specific phenotypic traits to their offspring

• appear similar to each other in appearance, respond similarly to the environment, and are homogenous for many traits that differentiate them from others members of the species

define hybrids

a genetically mixed organism that combines traits from two distinct parents

define the P generation

grandparents

define the F1 generation

parents

define the F2 generation

you and your siblings

Define homozygous

an organism that has 2 identical alleles for a gene

Define heterozygous

an organism that has two different alleles for a gene

define dominant allele

if the two alleles of an inherited pair differ, then one determines the organism’s appearance

define recessive allele

has no noticeable effect on the organisms appearance

define genotype

an allele pair

define phenotype

an observable trait

Define a monohybrid cross

investigates inheritance of a single gene/locus

Define Punnett Square

shows the 4 possible combinations of alleles after gametes combine

Explain how Mendel’s law of segregation describes the

inheritance of a single character.

Four hypotheses

1. alleles account for variations in inherited characters

2. for each character, an organism inherits two alleles of a gene, one from each parent

3. If the two alleles of an inherited pair differ, then one determines that organism’s appearance and the other has no noticeable effect on the organisms appearance

4. The law of segregation

Law of Segregation

Each parent produces gametes representing its two alleles in equal proportions. The alleles are segregated into separate gametes

describe the genetic relationships between homologous chromosomes

• carry alleles of the same genes at the same locations (loci)

Explain how Mendel’s law of independent assortment

applies to a dihybrid cross.

the alleles of a alleles of a pair segregate independently of other allele pairs during gamete formation

Explain how recessive disorders are inherited

the parents (heterozygotes) are carriers of the recessive allele for the disorder but are phenotypically normal

describe the inheritance patterns of incomplete dominance

the appearance of some F1 hybrids falls between the phenotypes of the two parental varieties

describe the inheritance patterns of multiple allelism

both alleles in a heterozygote are fully expressed

describe the inheritance patterns of codominance

both traits are expressed in heterozygotes

describe the inheritance patterns of pleiotropy

when one gene influences multiple characters

describe the inheritance patterns of polygenic inheritance

a single phenotypic character results from the additive effects of two or more gene (human skin tones)

Explain why human skin coloration is not sufficiently

explained by polygenic inheritance.

many traits are affected, in varying degrees, by both genetic and environmental factors

Define the chromosome theory of inheritance

• genes occupy specific loci on chromosomes

• chromosomes undergo segregation and independent assortment during meiosis

Explain the chromosomal basis of the laws of segregation and independent assortment.

• orientation of homologous chromosome pairs in

metaphase I → the law of independent assortment

• separation of homologous chromosomes in

anaphase I → the law of segregation

Explain how linked genes are inherited

they are located more closely together on a chromosome, it is more likely that they will be inherited together due to their physical proximity

explain how nonlinked genes are inherited

they get seperated during crossing over in meiosis, making inheritance appear independent

Explain how sex is genetically determined in humans.

• Males have XY sex chromosomes for the process of developing testes

• Females have XX sex chromosomes and the absence of the Y chromosome allows for the ovaries to develop

Describe patterns of sex-linked inheritance.

• A gene located on either sex chromosome is called a sex-linked gene.

• The X chromosome carries many X-linked genes that control traits unrelated to sex.

Structure of DNA

• one of the 2 strands is a DNA polynucleotide (Chain of nucleotides

• a nucleotide is made up of a phosphate group, 5 carbon sugar and a nitrogenous base (A,G,C,T)

• nucleotides are formed by a sugar phosphate backbone

Structure of RNA

• RNA nucleotide is made up of a phosphate group, 5 carbon sugars and a nitrogenous base (A,G,C,U)

Explain how the structure of DNA facilitates its

replication (e.g., complementary base pairing)

• H bonds between bases hold the strands together

• each base pairs with a complementary partner:

A→T and G→C (Both can go the other way)

What is the process of DNA replication

1. strands separate

2. each strand becomes a template for new free nucleotides

3. each new DNA helix has one old strand with one new strand

Transcription

• DNA turns into RNA in the nucleus under the direction of DNA

Translation

• RNA turns into Protein in the cytoplasm under the direction of RNA

How are the “languages” of DNA and RNA used to produce polypeptides

The genetic instructions for the amino acid sequence of

a polypeptide chain are written in mRNA (messenger

RNA) as a series of three-base “words” called codons.

Explain how eukaryotic RNA is processed before

leaving the nucleus.

• RNA splicing

  • introns are spliced out

  • exons are spliced together

  • and a cap and tail are added

What is the structure of tRNA?

a folded molecule bearing a base triplet called an anticodon and a specfic attachemnt site at the other end

What is the function of tRNA in the process of translation?

tRNA aides the ribosome attached to the mRNA and translates its message into a specific polypeptide.

What is the structure of ribosomes?

• Made of ribosomal RNA (rRNA) and proteins

• have binding sites for tRNA and mRNA

What is the function of Ribosomes?

holds mRNA and tRNAs together and connects amino acids from the tRNAs to the growing polypeptide chain.

Describe the step-by-step process by which

amino acids are added to a growing polypeptide

chain. (Elongation)

• mRNA moves one codon at a time relative to the ribosome

• as mRNA moves, a tRNA with a complementary anticodon pairs with each codon adding its amino acid to the growing polypeptide chain

• This continues until a stop codon reaches the ribosome’s A site (Termination)

Diagram of the overall process of transcription and translation

DNA —Transcription →RNA — Translation —> Polypeptide

What are the major types of mutations?

substitution, insertion, deletion

What are the causes of mutations?

• changes in the genetic information in a cell

  • errors in DNA replication or recombination

  • physical or chemical agents called mutagens

What are the potential consequences of mutations?

• could change an amino acid into a stop codon and would produce a prematurely terminated polypeptide

• could be deadly or innovative (for your benefit)

Define Evolution

the change in the heritable characteristics of biological populations over successive generations.

Explain why the concept of evolution is a theory

• It is widely accepted

• broader than a hypothesis

• generates new hypotheses

• is supported by thousands of scientific studies

How does the concept of homologies support evolution?

Structural and molecular homologies reveal evolutionary relationships

What is the definition of Homology?

similarity resulting from common ancestry.

How does the concept of fossil records support evolution?

it reveals the historical sequence in which organisms have evolved.

What is the definition of fossils?

the imprints or remains of organisms that lived in the past and document differences between past and present organisms

What is the definition of Artificial Selection?

when humans choose desirable traits and breed only organisms with those traits

How does the concept of artificial selection support evolution?

if artificial selection can bring about so much change within a short time frame, then natural selection could modify species considerably over many generations.

How does the concept of DNA evidence support evolution?

there is a universal genetic code for all the organisms

How are evolutionary trees used to represent ancestral relationships?

they show which species share the same ancestral traits, helping scientists see who branched off first

What is Darwins 1st Postulate of Natural Selection

Trait variation- individuals vary in traits within populations

What is Darwin’s 2nd postulate of natural selection

Traits are heritable- Variations are passed from parents to offspring

what is darwins 3rd postulate of natural selection

more offspring are produced than can survive

what is Darwin’s 4th postulate of natural selection

Survival and reproduction are nonrandom-advantageous traits= survival of the fittest

Explain the concept of fitness in an evolutionary sense

an organisms capacity for survival and reproduction in a specific environment.

what adaptations could lead to a greater fitness

higher disease resistance, predator evasion, speed, height, attractiveness to a mate etc

Explain why individuals cannot evolve

evolution happens to populations over generations

Explain why natural selection does not lead to perfect organisms.

• selection can act only on existing variations (new alleles arise from mutations)

• evolution co-opts existing structures and adapts them to new situations

What is an example of evolution?

Finches on the Galápagos Islands differed in size & shape of their beaks according to their diets (seeds, insects, fruit, nectar)

Bigger seeds=Bigger Beak

Explain how mutation produces genetic variation

the ultimate source of the genetic variation that serves as raw material for evolution.

Explain how sexual reproduction produces genetic variation

Fresh assortments of existing alleles (i.e., genetic variation) arise every generation from three random components of sexual reproduction:

1. crossing over in prophase I of meiosis

2. independent orientation of homologous chromosomes at metaphase I of meiosis

3. random fertilization.

What is the 1st main cause of evolutionary change

Natural Selection- differential survival and reproduction of individuals due to differences in phenotype

What is the 2nd main cause of evolutionary change

Genetic Drift- random changes in allele frequencies within a population