lab exam 2
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100 Terms
How is DNA packaged in a cell?
As a double-stranded DNA molecule.
What is a chromosome?
A structure within the nucleus made up of DNA.
What are homologous chromosomes?
Matched pairs of chromosomes.
What are sister chromatids?
Copies of a chromosome joined by a centromere.
How many chromosomes are in human somatic cells?
46 chromosomes (diploid).
How many chromosomes are in human gametes?
23 chromosomes (haploid).
What happens during fertilization?
Each gamete contributes one set of chromosomes, forming a diploid cell.
What are the two major phases of the cell cycle?
Interphase and the mitotic phase.
What occurs during interphase?
The cell grows and DNA is replicated.
What occurs during the mitotic phase?
The replicated DNA and cytoplasmic contents are separated.
What process partitions the cytoplasm in cell division?
Cytokinesis.
What phase involves cell growth and preparation for division?
Interphase.
What term describes chromosomes after DNA replication?
Sister chromatids.
What type of cells are diploid in humans?
Somatic cells.
What type of cells are haploid in humans?
Gametes.
How are homologous chromosomes paired?
By matching the same genes in the same order.
What is the genetic result of fertilization?
A diploid zygote.
How many homologous pairs do humans have?
23 pairs.
What structure joins sister chromatids?
The centromere.
What phase follows interphase in the cell cycle?
The mitotic phase.
What is the role of oxygen in cellular respiration?
It acts as the final electron acceptor in aerobic respiration.
What is the initial molecule broken down in respiration?
Glucose.
What molecule carries electrons to the ETC?
NADH.
What drives ATP production in the mitochondria?
Proton motive force.
What is the end product of the electron transport chain?
ATP (Adenosine triphosphate)
Where does the electron transport chain occur?
In the inner mitochondrial membrane.
What happens when O2 is unavailable in cellular respiration?
Anaerobic respiration or fermentation occurs.
What role does the electron transport chain (ETC) play?
It transfers electrons to create a proton gradient.
What enzyme synthesizes ATP?
ATP synthase.
What molecule starts the process of cellular respiration?
Glucose.
What happens to NADH in the electron transport chain?
It donates electrons.
What is produced when oxygen accepts electrons?
Water.
What molecule is reduced at the end of the ETC?
Oxygen.
What kind of respiration requires oxygen?
Aerobic respiration.
What is the role of the proton motive force?
Drives the synthesis of ATP.
What stage of respiration directly produces the most ATP?
The electron transport chain.
What type of molecule is ATP?
An energy carrier.
How is energy released from ATP?
By breaking the bond between its phosphate groups.
What forms when NADH donates its electrons?
NAD+ is regenerated.
What process generates NADH?
Glycolysis and the citric acid cycle.
Where does photosynthesis take place?
In chloroplasts.
What forms the third membrane layer in chloroplasts?
Stacks of thylakoids called grana.
What is embedded in the thylakoid membrane?
Pigments and proteins of the electron transport chain.
What do pigments do in photosynthesis?
Absorb specific wavelengths of light.
What are the two main reactions in photosynthesis?
Light-dependent and light-independent reactions.
What does PSII do in photosynthesis?
Absorbs sunlight and energizes electrons.
What happens to water molecules in PSII?
They are split to release oxygen and protons.
Where do energized electrons travel after PSII?
Through the electron transport chain to PSI.
What does PSI produce?
NADPH by reducing NADP+.
What drives ATP synthesis in chloroplasts?
The proton gradient across the thylakoid membrane.
What process converts light energy to chemical energy?
Light-dependent reactions.
What is the role of ATP synthase in photosynthesis?
Produces ATP using the proton gradient.
What inhibits electron flow from PSII?
DCMU.
What process is disrupted by sodium azide?
Mitochondrial respiration.
Why can chlamydomonas swim in the presence of DCMU?
It can use stored sugar for energy.
Why can’t chlamydomonas swim in the presence of sodium azide?
Inhibition of respiration prevents ATP production.
What energy molecule is produced during light-independent reactions?
Glucose.
What molecule is reduced to NADPH in PSI?
NADP+.
What is an example of a light-absorbing pigment?
Chlorophyll.
What is the initial energy source for photosynthesis?
Sunlight.
What is gene expression?
The process of converting DNA information into proteins.
How is gene expression controlled?
By regulatory mechanisms that turn genes on/off or adjust protein levels.
What is an operon?
A cluster of genes controlled by a single promoter in prokaryotes.
What binds to the promoter to initiate transcription?
RNA polymerase.
What is the function of the operator in an operon?
Acts as a binding site for a repressor protein.
What happens when a repressor binds the operator?
It blocks RNA polymerase, inhibiting transcription.
What is a repressible operon?
An operon that can be turned off when a repressor binds (e.g., trp operon).
What is an inducible operon?
An operon that is activated when an inducer inactivates the repressor (e.g., lac operon).
What is the preferred energy source for E. coli?
Glucose.
What does the lac operon enable E. coli to do?
Use lactose as an energy source.
What enzyme does the Z gene of the lac operon code for?
β-Galactosidase.
What role does CAP play in the lac operon?
Assists RNA polymerase binding to the promoter for high transcription.
What molecule regulates CAP activity?
Cyclic AMP (cAMP).
When does cAMP bind to CAP?
When glucose levels are low.
What happens when lactose binds the lac repressor?
The repressor is released from the operator, allowing transcription.
What happens when only glucose is present?
The repressor binds the operator, preventing transcription.
What two conditions allow high expression of the lac operon?
Low glucose and presence of lactose.
What color change indicates β-Gal activity with ONPG?
It turns yellow due to ortho-nitrophenol.
What is the role of RNA polymerase in transcription?
Synthesizes mRNA from the DNA template.
What is a "hunger signal" for E. coli indicating low glucose?
cAMP.
What are dominant traits?
Traits expressed if at least one dominant allele is present.
What are recessive traits?
Traits expressed only when both alleles are recessive.
What is incomplete dominance?
When two true-breeding parents produce an intermediate offspring.
What is codominance?
When more than one dominant allele is expressed equally in heterozygotes.
How are parents' genotypes used in Punnett squares?
To predict potential offspring genotypes.
What is a genotype ratio?
The ratio of different genetic combinations in offspring.
What is a phenotype ratio?
The ratio of observable traits in offspring.
What is a dihybrid cross?
A cross between two individuals observing two traits controlled by different genes.
What principle is visualized with dihybrid crosses?
Independent assortment.
When does independent assortment occur?
During metaphase I of meiosis.
What are model organisms?
Species studied to understand biological phenomena.
What traits make a good model organism?
Rapid development, short life span, easily manipulated, large offspring number.
Name examples of model organisms.
Mice, pigs, Drosophila, yeast, Arabidopsis.
Why is Arabidopsis a good model organism?
Fast life cycle and easily grown in limited space.
What is the purpose of a Punnett square?
To predict the probability of offspring genotypes and phenotypes.
What is observed in a 4:0 phenotype ratio?
All offspring show the dominant trait.
What does AA or Aa represent?
A dominant phenotype.
What genetic outcome occurs when crossing GG x Gg?
A genotype ratio of 2 GG: 2 Gg.
What does aa represent?
A recessive phenotype.
Why is meiosis important for genetic diversity?
it allows for independent assortment and recombination of alleles.