Biology Exam 3

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155 Terms
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DNA stores
genetic material
______ encodes the information to make polypeptides and RNA molecules
DNA (1)
________ is packaged in chromosomes and stored in the __________
DNA; nucleus
DNA ------> mRNA
The 5 levels of organization in DNA structure are
1. nucleotides, 2. single strand, 3. double helix, 4. chromosome, 5. genome
Chromosomes are composed of
DNA wound around histone proteins
Humans have how many chromosomes?
46 (23 pairs)
DNA nucleotide
phosphate group, sugar (deoxyribose), base
What are the bases of DNA?
Adenine, Thymine, Guanine, Cytosine
RNA nucleotides
phosphate group, sugar (ribose), base
What are the RNA bases?
Adenine, Uracil, Cytosine, Guanine
Nucleotide numbering system
Sugar carbons are 1' to 5' Hydroxyl group (-OH) attached to 3' carbon on sugar Phosphate attached to 5' carbon on sugar Base attached to 1' on carbon sugar
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single strand
phosphodiester bonds link nucleotides forms sugar-phosphate backbone bases project away from backbone has directionality-5' to 3'
In a nucleotide single strand
sugars and phosphates alternate 5' has free phosphate group 3' has free sugar group
double helix
-double stranded helix -strands run antiparallel -bases project toward the center
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complementary base pairing rules
A always pairs with T G always pairs with C
Adenine and Guanine
Cytosine and Thymine
more characteristics of the double helix
-uses base pairing rules -antiparallel strands (3' to 5' with 5' to 3')
consists of chromatin which is highly compacted DNA wrapped around histone proteins
To compact DNA and package into chromosomes:
1. double helix is wound into nucleosomes 2. nucleosomes to chromatin 3. 30 nm fiber 4. radial loop domain 5. compacted radial loop domain
2 broad forms of chromatin
euchromatin (less compacted DNA, active genes) and heterochromatin (highly compacted DNA, inactive genes)
all of an organism's genetic material
autosomal chromosomes
non-sex chromosomes 22 pairs in humans
sex chromosomes
Chromosomes that determine the sex of an individual 1 pair in humans
DNA replication
the process of making a copy of DNA for cell division
gamete production, cell renewal/growth, embryogenesis
DNA replication
DNA replication follows the __________ rule
during DNA replication
parental/original strands sperate and serve as template for the synthesis of a new/daughter strand
True or False: DNA replication is semi-conservative
Replication proceeds in _______ directions from an ________________________
both; origin of replication
origin of replication
Site where the replication of a DNA molecule begins.
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
steps of the formation and movement of the replication fork
1. DNA helicase unwinds DNA at replication fork 2. Single-strand binding proteins bound to prevent reforming double helix 3. DNA topoisomerase prevents tangling of DNA ahead of replication fork 4. DNA polymerase links nucleotides together to form DNA strands
DNA polymerase
Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
DNA polymerase adds nucleotides to which prime end?
A ______ primer is needed to start DNA replication
DNA primase
synthesizes short RNA primers
DNA replication process
On a strand 3' to 5': 1. RNA primer is laid down 2. leading strand of DNA is laid down to the replication fork From replication fork to origin (5' to 3') 1. RNA primer laid in front of origin of replication 2. Okazaki fragment is laid down from end to origin 3. process repeats to create the lagging strand
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leading strand
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction toward replication fork
lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.
Okazaki fragments
Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
True or False: The RNA primer can stay in the lagging strand.
FALSE: it must be replaced with DNA nucleotide AKA DNA polymerase
DNA ligase
Seals gaps between Okazaki fragments
True or False: DNA replication is very accurate
True, DNA polymerase has a proofreading mechanism to check for errors.
To fill in the 3' ends of the DNA strands, ___________ must be attached to the ends
Repeated DNA sequences at the ends of eukaryotic chromosomes. -prevent loss of genetic material -added by enzyme telomerase -as we grow, telomeres are shortened
the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes
the entire set of proteins expressed by a given cell or group of cells
segment of DNA that encodes a functional product -can encode polypeptides or functional RNA molecules
gene expression
1. DNA stores info in genes 2. Transcription of DNA to produce RNA copy of gene 3. mRNA, the copy of gene that will be used to make polypeptide 4. Translation produces polypeptide using mRNA
DNA to RNA to polypeptide
gene expression (transcription and translation)
Where does the gene expression processes take place?
Prokaryotic- cytosol and ribosomes Eukaryotic-takes place in nucleus and ribosomes (either free or ones attached on Rough ER)
synthesis of an RNA molecule from a DNA template
mRNA is complementary to
template strand (NONCODING STRAND)
mRNA sequence is the same as
non-template strand (CODING STRAND)
structure of a gene
promoter, regulatory sequence, terminator, transcribed region
Briefly describe the promoter, regulatory sequence, terminator, and transcribed region of a gene
promoter-START of transcription; place where RNA polymerase binds regulatory sequence-transcription factors (regulatory proteins) bind and control the rate of transcription terminator-END of transcription transcribed region-contains info that specifies an amino acid sequence; MIDDLE of gene
What are the three stages of transcription?
initiation, elongation, termination
Transcription initiation
sigma factor recognizes promoter and recruits RNA polymerase; DNA is unwound to separate strands; sigma factor released and RNA polymerase proceeds down DNA
Transcription Elongation
RNA polymerase continues down DNA strand using the template strand to make complementary RNA
Transcription Termination
When RNA polymerase reaches terminator, transcription stops & RNA chain is released
RNA processing in eukaryotes
-addition of 5' cap -addition of polyA tail -splicing AKA (Capping, Splicing, and tailing)
RNA splicing
Process by which the introns are removed from RNA transcripts and the remaining exons are joined together. (exons-expressed regions) (introns-intervening regions) -alternative splicing allows different proteins to be produced from the same gene
Organization of mRNA
ribosomal binding site-ribosome binding site, start codon-first amino acid, coding sequence-interchanging codons, stop codon-specifies stop
The three-base sequence of nucleotides in mRNA that specify a particular amino acid
The ______________ specifies amino acids within polypeptide
genetic code
The genetic code is _________________.
degenerate (same amino acid can be used repetitively)
tRNA contains what type of codon?
group of three bases on a tRNA molecule that are complementary to an mRNA codon -carries amino acid specified by codon (tRNA)
start codon
stop codons
Where does translation occur?
Characteristics of ribosomes
two subunits- Large and Small subunits composed of rRNA and proteins 3 sites where tRNA binds during translation: A, P, and E sites
________________ alter DNA sequence of a gene
Gene Mutation
A change in a gene or chromosome. -heritable change -source of variation for natural selection -most are harmful -genetically inherited diseases result from harmful mutations
point mutation
gene mutation in which a single base pair in DNA has been changed -caused by base substitution
Three types of point mutations
silent, missense, nonsense
silent mutation
A mutation that changes a single nucleotide, but does not change the amino acid created. -causes no change in protein structure or function
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missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid. -may change protein structure/function or may not -usually neutral or negative outcome
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nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein. -usually negative outcome
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indel mutation (base insertion or deletion)
a mutation in which one or more nucleotide pairs is added or deleted -may cause change in reading frame -addition or deletion shifts the reading frame and changes codons and resulting amino acids
frameshift mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide -changes amino acid sequence -negative outcome; changes protein structure/function
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mutations can also occur in _______________ regions
regulatory; may alter gene expression
Mutations occur in these type of cells:
germline and somatic
germline mutation
DNA alteration occurring in gametes that can be transmitted to offspring
somatic cell mutation
change within cells of the body, cannot be transmitted
spontaneous mutations
random change in the DNA due to errors in replication that occur without known cause
induced mutations
caused by environmental agents -chemical agents (cigarrete smoke or asbestos) -physical agents (UV light or X rays)
caused by accumulation of mutations that eventually cause excessive cell proliferation (rapid cell division) -around 7-10 mutations
progression of cancer
1. initial tumor cells- accumulate mutations that increase cell division 2. benign tumor-overgrowth of normal cells 3.malignant tumor-overgrowth of abnormal (cancerous) cells 4.metastasis-malignat cells enter bloodstream or lymphatics and spread throughout the body
Mutations in these cells promote cancer
proto-oncogenes and tumor suppressor cells
programmed cell death
promote normal cell division and growth -become oncogenes when develop gain-of-function mutation
overactive, abnormal genes that promote excessive cell division and prevent apoptosis
Normal signaling pathway that promotes cell division
1. growth factor signal binds to a receptor, leading to receptor activation 2. signal transduction pathway 3. proteins/transcription factors are activated that promote transcription of genes involved in cell division ONCOGENES AFFECT ANY OF THESE AREAS
tumor suppressor genes
genes who's loss of activity promotes excessive cell division -encode proteins that normally prevent cell division, promote apoptosis, and involved in DNA repair
tumor suppressor gene mutated in 50% of cancers -if DNA is damaged, p53 prevents cell division -if DNA is repaired, p53 cell divides normally -if DNA is not repaired, p53 promotes apoptosis
Chromosomes are inherited in ________ and occur as _________________ pairs
sets; homologous
homologous chromosomes
pair of chromosomes of the same type
diploid cells have ____ sets of chromosomes
haploid cells have ____ set of chromosomes
one (gametes)
cell cycle
series of events that cells go through as they grow and divide
Phases of the cell cycle
1. Interphase (G1, S, G2) 2. Mitosis (PMAT) 3. Cytokinesis (cell division)
part of eukaryotic cell division during which the cell nucleus divides -parent cell divides to produce 2 genetically identical daughter cells
S phase of cell cycle
chromosomes are replicated to produce a pair of sister chromatids
Steps of S phase
1. before mitosis, chromosomes replicate to make a pair of sister chromatids 2. chromosomes compact at beginning of mitosis
makeup of chromatin
held together by centromere kinetochore is the place where spindle fibers attach (near centromere)
Chromosomes vs chromatids
Chromosomes are made up of a pair of chromatids, while chromatids are two strands of a chromosome that divide during cell division.
spindle apparatus
responsible for organizing and sorting chromosomes during cell division -spindle fibers are microtubules of cytoskeleton that attach at kinetochore.
Stages of Mitosis
1. Prophase 2. Metaphase 3. Anaphase 4. Telophase/Cytokinesis
G1, S, and G2; all DNA is replicated
Chromosomes become visible and condense, nuclear envelop dissolves, spindle forms
chromatids attach to the spindle; nuclear envelope has completely broken down
Chromosomes line up (end to end) in the middle of the cell on metaphase plate
sister chromatids move to opposite ends of the cell
Telophase and Cytokinesis
Nucleus reforms (telophase) and cell is divided in two (cytokinesis) -splits by cleavage furrow
Cell division that produces reproductive cells in sexually reproducing organisms -produces 4 haploid gametes -Phases: Interphase, Meiosis 1 and Meiosis 2
Characteristics of phases of meiosis
Interphase: chromosomes duplicate Meiosis 1: homologous chromosomes separate Meiosis 2: sister chromatids separate
Differences between mitosis and meiosis
-Meiosis has 2 divisions; Mitosis has 1 division -Meiosis makes haploids; Mitosis makes diploids -Meiosis makes 4 cells; Mitosis makes 2 -Meiosis makes gametes; Mitosis makes somatic -Meiosis makes genetically different daughter cells; Mitosis makes identical daughter cells
Stages of Meiosis 1
Prophase 1, Prometaphase 1, Metaphase 1, Anaphase 1, Telophase/Cytokinesis 1 -play same roles as mitosis phases, except they use bivalents and crossing over. -during this metaphase, chromosomes line up side by side -results in 2 haploid cells
Stages of Meiosis 2
Prophase 2, Prometaphase 2, Metaphase 2, Anaphase 2, Telophase/Cytokinesis 2 -same roles as mitosis -results in 4 haploid cells
production of gametes (spermatogenesis and oogenesis)
Formation of sperm -begins at sexual maturity -produces 4 functional gametes 1. spermatogonia, 2.primary spermatocyte, 3.secondary spermatocyte, 4.spermatids, 5.sperm cells
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Egg production -starts at fetal development -born with primary oocytes in prophase 1 -each month, 1 primary oocyte continues with meiosis -gives rise to only 1 functional gamete 1. oogonia, 2.primary oocyte, 3.secondary oocyte, 4. ovum, 5. polar bodies
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Variations in Chromosome Number
euploids, polyploids, and aneuploids
chromosomes occur in complete sets EX) haploids have 1 set and Diploids have 2 sets
3 or more sets of chromosomes EX) triploids-3, and tetraploid-4
Abnormal number of chromosomes. EX) trisomy-extra copy and monosomy-missing copy -conditions result from chromosomes not separating properly; most are not compatible with life -occurs in sex chromosomes too and usually have better quality of life
Aneuploidy results from
chromosomes do not separate properly during cell division
Chromosome numbers are _________ between species, but _________ within species
different; same EX) Humans 23 pairs but Dogs have 39
Mendel's Laws of Inheritance
law of equal segregation and law of independent assortment
Gregor Mendel
Father of genetics -pea plant experiments investigated inheritance -it was believed all lines were true breeding (pure bred) -experiments showed law of segregation and law of independent assortment -3:1 ratio
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law of equal segregation
a gene has two copies and during gamete production the gene copies separate equally
Characteristics of Mendel's law of equal segregation
1. an individual carries 2 alleles for a given character 2. traits exist in 2 forms: dominant and recessive 3. alleles segregate equally during gamete formation and each gamete receives 1 allele 4. 1 male gamete and 1 female gamete randomly combine during fertilization
The chromosomal basis of equal allele segregation
1. Chromosomes replicate, and cell progresses to metaphase of meiosis I. 2. Homologs segregate into separate cells during meiosis I. 3. Sister chromatids separate during meiosis II to produce 4 haploid cells.
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genetic makeup of an organism -homozygous-2 identical alleles -heterozygos-2 different alleles
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Allele that is most common in nature is the
wild/normal type
Allele that does not occur commonly in nature is the
mutant/affected type
observable characteristics of an organism
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_____________ is a tool used to predict the outcome of genetic crosses
punnet square
the chance of a particular outcome in genetics -number of times the outcome could occur
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law of independent assortment
alleles of different genes assort independently during gamete formation
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the chromosomal basis of independent assortment
Alignment of homologs can occur in more than one way during metaphase 1 (shown in picture)
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Simple single gene inheritance in humans
Most genetic traits in humans are determined by interactions between several genes or between genes and the environment Traits include: genetically inherited disorders (cystic fibrosis etc.), ABO blood groups, color vision vs colorblindness
A diagram that shows the occurrence of a genetic trait in several generations of a family. -circles females, squares males, colored affected by trait, open unaffected by trait
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autosomal recessive traits
traits that are only displayed if you have two copies of the recessive allele of a gene -affected ex: bb -unaffected ex: Bb or BB usually have unaffected parents
autosomal dominant traits
Affected individuals have at least one affected dominant allele -affected ex: BB or Bb -unaffected ex: bb usually has an affected parent
Tay Sachs and Cystic fibrosis
autosomal recessive traits
Dwarfism and Huntington disease
autosomal dominant traits
Determining gender
-Males XY, Females XX
X linked recessive traits
-occur more often in males -males have heterozygous mothers -affected females MUST have affected FATHER EX color blindness
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