Test 3 Ojectives

Question 1

Describe the cellular organization of genetic material

Answer 1

•DNA molecules in a cell are packaged into chromosomes.
•Chromatin is uncondensed complex of DNA.
Chromosomes is condensed chromatin

Question 2

Describe the stages of the cell cycle (G1, S, G2, M/C)

a.Know key events that happen in each stage

Answer 2

• G1 phase the cell grows and does normal cell functions
• S phase the cell copies it’s DNA (chromosomes) in preparation. For cell division. Each duplicated chromosome has two sister chromatids
• G2 phase the cell keeps growing produces more organelles in anticipation of cell division.
• Mitosis is the division of the nucleus and the nuclear material.
• Cytokinesis is the physical division of the cytoplasm and its components into two distinct daughter cells

Question 3

Evaluate where a cell spends most of its time in the cell cycle

Answer 3

• the cell spends most of its time in interphase

* Metaphase is the longest stage of mitosis

Question 4

Distinguish between

cytokinesis in plant and animal cells

Answer 4

• cytokinesis in a plant cel involves the formation of a cell plate, as material for a new cell wall is laid down between two poles of the cell
• Cytokines in an animal cell involves a ring of actin microfilaments which serve as a draw string that pinches the cell around the middle to for a cleavage furrow—shallow groove in cell surface

Question 5

Explain the result of mitosis

Answer 5

•produces two genetically identical daughter cells

Stages are prophase, metaphase, anaphase, telophase

Question 6

Explain how offspring acquire genes from parents

Answer 6

•through reproductions. either asexual or sexual reproduction.

Question 7

Compare asexual and sexual reproduction

Answer 7

• asexual reproduction is one parent that passes copies of all its genes to offspring without fusion of gametes; mitosis in eukaryotes or binary fission in prokaryotes; is genetically identical offspring, or clones; only when there is a mutation is there a variation in the offspring.
• sexual reproduction usually involves two parents which gives rise to genetically unique offspring, regardless of DNA mutations; completed by two cells (gametes) which fuse together to form a single cell called a zygote; the gametes have to have half genetic information so the offspring doesn’t continually grow in genetic information; germ cells go through meiosis do accomplish this half the number of chromosomes.

Question 8

Distinguish between haploid and diploid

Answer 8

• (n) haploid is one set (half the number) of chromosomes. a condition when a cell has only one of each kind of chromosome; this never occurs in human cells except for gametes (sperm and egg), which have a haploid number of chromosomes (23)
• (2n) two sets of chromosomes; parental cells have two of every kind of chromosome (one is maternal and the other paternal in origin)-use the expression 2n to denote the two of every kind of chromosome; means the diploid parental number is 46 chromosome (23 from mom and 23 from dad)

Question 9

Distinguish between chromatin, chromosome, chromatid, and homologous chromosomes (homologs)

Answer 9

• Chromatin is uncondensed (less condensed) complex of DNA + protein (histones); condenses during cell division; DNA carries hundreds to a few thousand genes
• Chromosomes consist of condensed chromatin; replicated (duplicated) chromosome which is two sister chromatids; attached via centromere- which is a specific DNA sequence where chromatids are attached most closely to one another by protein structure known as kinetochore
• Chromatid is sister chromatid that is joined copies of the original chromosome (one half of a replicated chromosome)
• homologous chromosomes (homologs) is matching chromosomes (one from each parent) that carry genes fro the same type of traits

Question 10

Distinguish between autosomes and sex chromosomes

Answer 10

• autosomes are most of the chromosomes contain information that does not determine
• sex chromosomes are a couple of chromosomes (X and Y) contain information that determines gender

Question 11

Explain a karyotype

Answer 11

•is the visual display of condensed chromosomes arranged in homologous pairs

Question 12

Distinguish between oogenesis and spermatogenesis

Answer 12

• oogenesis is the germ line cells in women only complete the ful meiotic division iIF they are fertilized by the sperm; meiosis in women produces up to four haploid gamets, but only one of them will become a viable egg cell (this assumes that it will be fertilizedx since it does not actually finish meiosis until it is fertilized by a sperm.
• spermatogenesis meiosis in me and produces four haploid gametes which will eventually become four viable sperm.

Question 13

Explain how meiosis reduces the number of chromosomes sets from diploid to haploid

Answer 13

•it goes through 2 rounds of meiosis; it reduces the number of homologous pairs on anaphase I then separates those pairs in anaphase II

Question 14

Describe the stages of meiosis

a.Be able to distinguish between events in meiosis I and meiosis II

Answer 14

• Prophase I- the nuclear membrane disintegrates; chromatin condenses into chromosomes; spindel forms and connects to chromosomes; synapsis where homologous chromosomes pair up and are connected together through a special protein structure called the synaptonemal complex; crossing over when the homologous chromosomes exchange equivalent peices of their chromosome arms containing alleles and recombinant chromosomes (that carry genes from two different parents)
• Metaphase I- homologous pairs line up on the mataphase plate; pairs randomly line up through independent assortment and helps create new daughter cells with varied collections of chromosomes
• Anaphase I - homologous pairs are separated from each other and moeved to opposite poles; each pole must receive one chromosome from each homologous pair (each chromosome also has a copy or sister chromatid still attached at the kinetochore in the centromere region)
• Telophase I and cytokinesis - two new cells form, each containing a haploid number of chromosomes (each chromosome consists of two sister chromatids through they are no longer identical due to crossing over); cytokinesis is similar to mitosis; chromosomes may or may not decondense and nuclear membrane may or may not reform; no duplication of chromosomes occurs before the next phase
• Prophase II -chromosomes fully condense; nuclear membrane disappears (if it reformed after telophase I); spindle fibers connect to kinetochore on individual sister chromatids
• Metaphas II - chromosomes line up at metaphase plate
• Anaphase II - sister chromatids separate and are pulled to opposite sides of the cell ( at this point they are called daughter chromosomes or unduplicated chromosomes)
• Telophase II and cytokinesis - chromosomes decondense and nuclear membrane reforms; cytokinesis proceeds to divide cytoplasm into two new cells; since meiosis I produced two daughter cells which proceeded into meiosis II, at the end of meiosis II we produce a total of four haploid, genetically unique cells.

Question 15

Compare and contrast mitosis and meiosis

Answer 15

• Compare - they both have the phases prophase, metaphase, anaphase, telophase and cytokinesis (even though what happens in the phases are slightly different)
• Mitosis - produces 2 genetically identical daughter cells; produces diploid daughter cells; contains one round of cell division; occurs in somatic cells and unicellular organisms (for asexual reproduction); enables multicellular adult to arise from zygote; produces cells for growth, repair and in some species, asexual reproduction.
• Meiosis - produces 4 genetically unique daughter cells; produces haploid daughter cells; contains two rounds of cell division’ occurs only in germ line cells (for sexual reproduction); produces gametes, reduces number of chromosomes by half and introduces genetic variability among gametes

Question 16

Explain the evolutionary advantage created by meiosis and how it is
created

Answer 16

• independent assortment of aleles on different chromosomes during meiosisI ensures genetic diversity in gametes (and offspring)
• crossing over in prophase I ensures genetic diversity in gametes (and offspring)
• random fertilization of sperm and egg ensure diverse combinations of alleles in offspring

Question 17

Distinguish between dominant and recessive, homozygous and heterozygous, true breeding and hybrid, allele and gene, phenotype and genotype

Answer 17

• Dominant allele masks or covers up the presence of other alleles; the dominant allele is fully expressed in the phenotype of a heterozygote = what we “see”
• recessive allele is the alleles that are masked; recessive alleles are hidden, we don’t “see” their effect on organisms’s phenotype in a heterozygote only in a homozygous recessive
• homozygous is an organism with two identical alleles for a trait; homozygous dominant or homozygous recessive
• heterozygous is an organism that has two different alleles for a gene; both dominant and recessive for the same gene
• true-breeding is an organism that produces offspring of the same variety over many generations when they self-fertilize; organisms with identical alleles for a paticular trait (PP or pp)
• Hybrid is a mating (crossing) of 2 contrasting true-breeding varieties
• allele is an alternative forms of a gene
• genes discrete regions of DNA on a chromosome that code for specific traits
• phenotype is the physical appearance; description of characteristic/trait
• genotype is the genetic makeup; listing of the 2 alleles; the organism inherits two alleles, one from each parent

Question 18

Describe the standard conventions for describing alleles (ie. Capital and lower case)

Answer 18

• use capital letter for a dominant allele

* use lowercase letter for a recessive allele

Question 19

Discuss what organism Mendel used and how he used it to work out the laws of segregation and independent assortment

Answer 19

• Mendel discovered the basic principles of heredity by breeding garden peas
• the advantages of pea plants - many varieties with distinct heritable features; short generation time; large number of offspring from each mating; mating can be controlled.

Question 20

State the laws of segregation and independent assortment, and discuss the implications of these laws as they relate to crosses

Answer 20

• Laws of segregation - the two alleles of a gene segregate during meiosis and each gamete carries only one allele of each pair; explains the 3:1 ratio of the F2 phenotypes observed monohybrids self-pollinate
• Law of independent assortment - each pair of alleles segregates independently of each other pair of alleles during gamete formation.

Question 21

Describe the P, F1, and F2 generations

Answer 21

• P (parental) generation - the true-breeding varieties
• F1 (filial) generation - the hybrid offspring (Pp) of the P generation
• F2 generation - offspring that result when the hybrid offspring of the F1 generation either self-pollinate of cross-pollinate with out F1 hybrids

Question 22

Be able to solve monohybrid or single factor crosses

Answer 22

•PPxpp is 100% Pp (using a punnet square)

Question 23

Be able to solve dihybrid or double factor crosses

Answer 23

• IE YyRr x YyRr
• make sure to make a allele key, with assigned letters
• punnet square

Question 24

Distinguish between non-linked and linked genes

a. Distinguish between sex linked and linked genes
b. Distinguish between X-linked and Y-linked genes

Answer 24

• Linked genes is the genes on the same part of the chromosome. So when the crossing over happens they cross over together
• Non-linked is on different spot or all together different chromosome
• sex linked means the allele is located on the sex chromosomes. Either the X or the Y chromosome.
• X-linked is when it is on the X sex chromosome. Female can be a carrier but she would need two alleles to show on a phenotype while the male only needs one from the mother to show in the phenotype.
• Y-linked genes is only located on the Y sex chromosome and only men can have it and pass it down to their sons.

Question 25

Be able to figure out the different kinds of gametes for a given genotype

Answer 25

•punnet square with mother and father alleles

Question 26

Distinguish between incomplete dominance and codominance

Answer 26

• Incomplete dominance - when heterozygote has a phenotype intermediate between those of the two parents (red flower and white flower makes a pink flower)
• Codominance - condition in which two alleles of a locus are expressed in heterozygote. (reddish and white hare colors are expressed independently of each other so having hair by hair difference)

Question 27

Discuss types of inheritance for a single gene (incomplete dominance, codominance, multiple alleles, and pleiotropy)

Answer 27

• multiple alleles - when 3 or more alleles for a given locus (a gene) exists in a given population (ie blood type)
• pleiotropy - ability of a single gene to have multiple affects on several phenotypic characteristics (ie symptoms of cystic fibrosis)
• Codominance - condition in which two alleles of a locus are expressed in heterozygote.
• Incomplete dominance - when heterozygote has a phenotype intermediate between those of the two parents

Question 28

Discuss types of inheritance for two or more genes (epistasis, polygenic inheritance)

Answer 28

• epistasis - a gene at one locus alters the phenotypic expression of a gene at a second locus, prevention or masking of a phenotype (ie labrador retrievers coat color)
• Polygenic inheritance - alleles at several loci affect a single phenotypic trait expression (ie skin color in humans)

Question 29

Distinguish between the blood types and be able to solve genetic problems

Answer 29

• three alleles for blood type IA, IB, i.
• alleles IAIA or IAIO = genotypes AA or AO = phenotypes Type A
• Allels IBIB or IBIO = genotype BB or BO = phenotype Type B
• Allele IAIB = genotype AB = phenotype type AB
• Allele ii or IOIO = genotype OO = phenotype type O

Question 30

Distinguish between genetic disorder and a genetic condition (know the examples discussed in lecture)

Answer 30

• Genetic conditions is when a recessive inherited condition shows up only in individuals homozygous for the allele (ie albinism)
• Genetic disorder is when the allele change that would affect the ability of a person to survive under normal circumstances and without treatment. (ie tay-sachs disease - dysfunctional enzyme causes an accumulation of lipids in the brain; cystic fibrosis - allele results in defective or absentchloride transport channels in plasma membranse; sickle-cell disease is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells)

Question 31

Define a carrier

Answer 31

•Carrier is heterozygous individuals who carry the recessive allele but are phenotypically normal

Question 32

Be able to find probabilities

Answer 32

• Multiplication rule - the probability that two or more independent events will occur together is the product of their individual probabilities (ie the probability of homozygous recessive wrinkled pea offspring if both parents are heterozygous round pea)
• Addition rule - the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities (ie probability of heterozygous offspring if both parents are heterozygous round pea)

Question 33

Be able to analyze pedigrees and discuss the inheritance patterns

Answer 33

•pedigree is a chart that shows how a trait and the genes that control it are inherited within a family.

Question 34

Discuss the historical contribution and importance for the following: Fred Griffith, Oswald Avery, Colin MacLeod and Maclyn McCarty, Alfred Hershey and Martha Chase, Erwin Chargaff, Rosalind Franklin, James Watson and Francis Crick

Answer 34

• Fred Griffith and streptococcus pneumonia experiments; inquiry: can a genetic trait be transferred between different bacteria strains?; discovery: transformation (a change in genotype and phenotype due to assimilation of foreign DNA); How this was determined: Griffith mixed heat-killed remains of pathogenic strain with living cells of the harmless strain, some living cells became pathogenic; Conclusion: harmless cells had been transformed into pathogenic cells by an unknown heritable substance
• Oswald Avery, Colin MacLeod and Maclyn McCarty - discovery: DNA was responsible for the transformation observed by Griffith; repeated Griffith experiment with treated pathogenic samples and tested the samples for its ability to trasform live nonpathogenic bacteria; result; only when DNA was left active did transformation occur; the sample that inactivated DNA had only nonpathogenic cells no transformation occurred to form pathogenic strain.
• Alfred Hershey and Martha Chase (the great kitchen blender experiment) - discovery: bacteriophages (viruses that infect bacteria) inject their DNA into bacterial cells; determined by using radioactive sulfur to trace the fate of protein and radioactive phosphorus to trace the fate of DNA; result When proteins were labeled radioactivity remained outside the cells; but when DNA was labeled radioactivity was found inside the cells
• Erwin Chargaff reported that DNA composition varies from one species to the next- in any species the number of A and T bases are equal and the number of G and C bases are equal; base paring rules: A pairs with T and C pairs with G
• Rosalind Franklin crucial contributor to the discovery of DNA’s structure - discovery: X-ray diffraction (crystallography) revealed that DNA had repeating units and was therefor helical; she inferred from the patterns that the bases were stacked like rungs of a ladder, and the sugar phosphate backbones were on the outside of the DNA molecule
• James Watson and Francis Crick published material on the physical structure of DNA; using Franklin’s model, Watson and Crick put all the pieces together, determine that DNA is a double helix with specific base pairing

Question 35

Explain complimentary base pairing

Answer 35

•Complimentary base pairing is when the A and T pair and C and G pair

Question 36

Explain the characteristics of DNA

Answer 36

• DNA’s building blocks is made up of nucleotides
• Nucleotides
• Double helix is antiparellel (3’-5’ and 5’-3’ on the other side) and complementary (2 strands, each stores the information necessary to reconstruct the other)

Question 37

Indicate the components of a nucleotide

Answer 37

•consist of - 5-C sugar; deoxyribose (backbone–side rails of the ladder); phosphate (backbone–side rails of the ladder); nitrogenous bases (rungs of the ladder): purines (Adenine(A) and Guanine(G)) and pyrimidine (Thymine(T) and Cytosine(C))

Question 38

Distinguish between purines and pyrimidines

Answer 38

• purines have two organic rings Adenine(A) and Guanine(G)

* pyrimidines have one organic ring Thymine(T) and Cytosine(C)

Question 39

Distinguish between semiconservative, conservative, and dispersive models of DNA replication

Answer 39

• semiconservative model is when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand
• conservative model is when the two parent strands rejoin
• dispersive model is when each strand is mixed of the old and new.

Question 40

Distinguish between the enzymes involved in DNA replication

Answer 40

• DNA polymerase is the main enzyme involved in the replication of DNA via adding nucleotides
• DNA helicase is the enzymes that untwist the double helix and the replication forks; makes the strands available as template strands
• topoisomerase is the enzymes that break and rejoin the parent DNA ahead of the replication fork relieving the strain caused by unwinding (help keep DNA form “tangling” once unwound)
• primase is the enxyme that synthesizes RNA primer (needed to initiate DNA synthesis)
• DNA polymerase III is the enzymes that synthesis new DNA by adding nucleotides to preexisting chain.
• DNA ligase is the enzyme that joins the sugar phosphate backbones of the Okazaki fragments on the lagging strand

Question 41

Explain how a single strand of DNA is able to serve as a template for the synthesis of another strand

Answer 41

•Since they are complementary and A and T only pair and G and C only pair, one strand can serve as a template to allow for replication since there is one type of combination per letter

Question 42

Explain the results of DNA replication

Answer 42

•When a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand

Question 43

Discuss the flow of genetic information

Answer 43

• DNA
• Transcription in nucleus
• RNA (mRNA)
• Translation ribosomes in cytoplasm
• Protein (polypeptide)

Question 44

Describe the structure and function of the different types of RNA

Answer 44

• mRNA - is the messager RNA that carries a genetic message from the DNA to the protein synthesizing machinery of the cell.
• rRNA is the ribosome RNA used in translation
• tRNA is the RNA that has a triplet anti-codons used in translation to transfer the RNA code to amino acids to create a protein

Question 45

Describe protein synthesis

Answer 45

• Transcription: DNA –> mRNA; in the nucleus
• Transcrition has three stages: initiation - RNA polymerase II separates DNA and joins together RNA nucleotides complementary to the DNA template strand, promoter is recognized at the TATA box and RNA polymerase II binds; elongations - RNA polymerase continues to unwind helix adding RNA nucleotides; termination - transcript is relased upon reaching the polyadenylation signal (AAUAAA) and the RNA polymerase detaches from the DNA
• RNA is the processed with the addition of 5’cap and a poly-A tail; RNA is spliced leaving the exons and the introns stay in the nucleus
• Translation: mRNA –> protein; in the cytoplasm
• Translation components: tRNA with anticodon and polypeptide attached to the other end, ribosomes (consists of protein and rRNA), and requires ATP
• Three steps in translation: initiation - small ribosomal unit binds to mRNA, initiator tRNA with anticodon UAC brings in MET amino acid, large subunit assembles hydrolyzing GTP; elongation - adding amino acids to growing polypetide , codon recognition when tRNA with next anticodon base pair to mRNA enters Asite, peptide bond formation is when GTP used to form peptide bond between amino acids elongating polypetide, and translocation is when the ribosome translocates tRNA in A site to P site, and RNA to p site moved to E site where it is released; termination - ribosome reaches stop codon (UAG, UAA, or UGA) on mRNA and the Asite accepts release protein factor that stimulates hydrolysis of polypetide from tRNA and P site, ribosome assembly dissociates.

Question 46

Be able to diagram the DNA strand, mRNA complement, tRNA complement, or protein (amino acids) for a given sequence

Answer 46

•

Question 47

Where does protein synthesis take place?

Answer 47

• Transcription: DNA –> mRNA; in the nucleus

* Translation: mRNA –> protein; in the cytoplasm

Question 48

Describe the role ribosomes play in protein synthesis

Answer 48

•the ribosome basically is the place where the mRNA is translated into an amino acid sequence within the cytoplasm

Question 49

Compare and contrast transcription and translation

Answer 49

• the two have the same step of initiation, elongation, and termination
• transcription is the creation of mRNA
• translation is the translation of mRNA into amino acid chain.

Question 50

Explain translocation

Answer 50

•translocation is when the ribosome translocates tRNA in A site to P site, and RNA in P site moved to E site where it is released.

Question 51

Compare and contrast codons and anticodons

Answer 51

• codons are the triplet code on the mRNA that signals for a specific tRNA with an amino acid
• anticodon is the triplet code on the tRNA that is complementary to the codons on the mRNA
• they are both triplet codes, complementary to one another, anti parallel

Question 52

Describe the building blocks of proteins and the type of bond between these building blocks

Answer 52

• polypetide bonds are the bonds that hold the amino acids together.
• amino acids are the building blocks of the proteins