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bio test 3 Flashcards

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1
Q

What is an autosome and a sex chromosome?

A

Autosome: 22 pairs of chromosomes (in humans)
Sex Chromosomes: 1 pair in humans (XY or XX)

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2
Q

What is the difference between a chromosome and chromatid?

A

Chromosome: A chromosome is a long DNA molecule that contains genetic information. In eukaryotic cells, chromosomes are found in the nucleus.
Chromatids: A chromatid is one-half of two identical copies of a replicated chromosome. Each chromatid is a single, continuous DNA molecule

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3
Q

Be able to describe the general events during the cell cycle (all four stages). Explain why those
events are important/necessary.

A

G1 (gap 1): Cell grows/performs normal functions- important for DNA synthesis
S: DNA is replicated, 2 sister chromatids for each chromosome
G2 (gap 2): Cell growth- prepares for mitosis, ensures DNA is accurately replicated, and repairs any DNA damage
M (mitosis): cell divides copied DNA and cytoplasm to create two new cells (ensure genetic material distribution)

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4
Q

What parts of the cell cycle make up interphase?

A

G1, S, and G2

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5
Q

What is the role of the gap phases in the cell cycle?

A

g1: ensures cell is ready for DNA replication
g2: checkpoint to ensure DNA replication was successful and repairs any DNA damage before mitosis

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6
Q

What happens during S-phase? Why is this step important for cell division?

A

Happens: DNA replication occurs, each chromosome is duplicated to produce sister chromatids
Important: ensures each daughter cell will have an identical set of chromosomes after cell division

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7
Q

What happens during M-phase? Why is this step important for cell division?

A

Happens: Mitosis- duplicated chromosomes are separated into two new nuclei. Cytokinesis divides the cytoplasm, resulting in two distinct daughter cells
Important: for distributing identical genetic material to each new cell

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8
Q

Be able to describe the duplication (synthesis) of chromosomes (DNA) and then their division
during mitosis; know when sister chromatids are made and split.

A

Synthesis (S-phase): DNA is replicated to form sister chromatids connected at a centromere.

Mitosis:
Prophase: Chromosomes condense and become visible.

Metaphase: Chromosomes align at the cell’s equator.

Anaphase: Sister chromatids are pulled apart to opposite poles.

Telophase: Nuclear membranes form around each set of chromosomes, resulting in two nuclei.

Cytokinesis: The cytoplasm divides, creating two daughter cells.

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9
Q

Know when mitosis occurs, and what kind of cells go through mitosis. Also know general events
and outcomes of mitosis, and why this is important for organisms.

A

Occurs: in somatic (non-reproductive) cells of multicellular organisms
Cells that go through: Somatic cells
Outcomes: two genetically identical daughter cells
Important: Growth, tissue repair, asexual reduction

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10
Q

Describe ploidy. How do you determine ploidy? If given a cell with a certain ploidy and
chromosome number (example: 2n=8), be able to draw it in every phase of mitosis and meiosis.

A

Describe: Ploidy refers to the number of sets of chromosomes in a cell
Determine: count the number of chromosome sets.

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11
Q

What kinds of ploidy are there

A

Diploid (2n): Two sets of chromosomes (one from each parent)
Haploid (n): One set of chromosomes

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12
Q

Be able to describe how meiosis is different than mitosis

A

Mitosis: Produces two genetically identical diploid daughter cells.

Meiosis: Produces four genetically diverse haploid gametes (sperm or egg cells). It involves two rounds of cell division (Meiosis I and II) and includes processes like crossing over and independent assortment.

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13
Q

What are the roles of kinetochores and kinetochore-microtubules in mitosis? What would happen if
there was an unattached chromosome when anaphase starts?

A

Kinetochores: Protein structures on the chromosome that attach to spindle microtubules.

Kinetochore-Microtubules: Microtubules that connect the kinetochores to the spindle poles, facilitating chromosome movement. If a chromosome is unattached when anaphase starts, it could result in unequal distribution of genetic material, leading to aneuploidy.

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14
Q

What is the purpose of cytokinesis?

A

purpose: divides the cytoplasm of a parental cell into two daughter cell
ensures: ensures daughter cell receives necessary cellular components to survive and function properly

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15
Q

Describe the duplication (synthesis) of chromosomes (DNA) and then their division during both mitosis and meiosis; know when sister chromatids are made and split.

A

Describe: During the S-phase of the cell cycle, DNA replication occurs. Each chromosome is duplicated to form two sister chromatids joined at the centromere.
Mitosis:
Prophase: Chromosomes condense and become visible.
Metaphase: Chromosomes align at the cell’s equator.
Anaphase: Sister chromatids are pulled apart to opposite poles.
Telophase: Chromatids reach the poles, nuclear membranes reform, and the cell divides (cytokinesis), resulting in two identical daughter cells.
Meiosis: Prophase I: Homologous chromosomes pair and exchange segments (crossing over).
Metaphase I: Homologous chromosomes align at the equator.
Anaphase I: Homologous chromosomes are pulled apart.
Telophase I: Two haploid cells form.
Meiosis II: Similar to mitosis, sister chromatids are separated.
Prophase II: Chromosomes condense again.
Metaphase II: Chromosomes align at the equator.
Anaphase II: Sister chromatids are pulled apart.
Telophase II: Four haploid cells form, each genetically unique.

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16
Q

Know when mitosis and meiosis occur, and what kind of cells go through mitosis and meiosis. Also know general events and outcomes of mitosis and meiosis, and why this is important for organisms.

A

Mitosis: Occurs in somatic (body) cells for growth, tissue repair, and asexual reproduction.
outcome: Results in two genetically identical diploid daughter cells
Meiosis: Occurs in germ cells to produce gametes (sperm and egg) for sexual reproduction.
outcome: Results in four genetically diverse haploid gametes

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17
Q

Differences Between Meiosis and Mitosis

A

Meiosis: Involves two divisions, producing genetically diverse haploid cells. Homologous chromosomes pair and separate.

Mitosis: Single division producing identical diploid cells. No pairing of homologous chromosomes.

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18
Q

Consequences of Meiosis:

A

Genetic Variation: Meiosis introduces genetic diversity through crossing over and independent assortment.

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19
Q

Evolutionary Perspective on Sex

A

Generates genetic diversity, which can enhance adaptability and survival in changing environments

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20
Q

Nondisjunction: definition, outcome and some syndromes

A

Definition: Failure of chromosomes to separate properly during meiosis.

Outcome: Results in aneuploidy (abnormal number of chromosomes).

Syndromes: Down syndrome, Turner syndrome, Klinefelter syndrome.

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21
Q

Crossing Over (Recombination): occurs when and consequences

A

Occurs During: Prophase I of meiosis.

Consequences: Exchange of genetic material between homologous chromosomes increases genetic diversity

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22
Q

How does recombination contribute to accurate segregation of homologs?

A

Accurate Segregation: Recombination helps ensure homologous chromosomes segregate accurately during meiosis I.

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23
Q

What role does homologous recombination play in generating genetic diversity?

A

Creates new combinations of alleles, contributing to genetic variation.

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24
Q

What are the roles of kinetochores and kinetochore-microtubules in mitosis? What would happen if there was an unattached chromosome when anaphase starts?

A

Function: Attach to chromosomes and pull them apart during anaphase.

Unattached Chromosome: Can lead to unequal distribution of genetic material.

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25
Purpose of Cytokinesis:
Definition: Division of the cytoplasm, creating two distinct daughter cells
26
Why is pairing of homologous chromosomes so important in meiosis?
Ensures Proper Segregation: Correctly pairs and separates homologous chromosomes
27
What are the major processes occurring in meiosis I and meiosis II?
Meiosis I: Homologous chromosomes separate. Meiosis II: Sister chromatids separate, similar to mitosis.
28
How can chromosomes be altered?
Mutations, Deletions (Loss of a chromosome segment), Duplications, Inversions, Translocations, Nondisjunction
29
What is the difference between aneuploidy and polyploidy? How can these affect humans? Other species?
Aneuploidy: The presence of an abnormal number of chromosomes (e.g., trisomy 21) Humans: developmental disorders/syndromes. Other Species: Can be lethal or cause developmental abnormalities. Polyploidy: The presence of more than two sets of chromosomes (e.g., triploid (3n), tetraploid (4n)). Humans: Generally not viable in humans, leading to miscarriage. Other Species: Common in plants, can result in larger and more robust species.
30
How can aneuploidy occur?
Typically results from nondisjunction during meiosis or mitosis, where chromosomes fail to separate properly, leading to cells with too many or too few chromosomes
31
What is a Gene? What is an Allele?
Gene: A segment of DNA that contains the instructions for making a specific protein or set of proteins. ex: determines flower color Allele: Different versions of a gene that can exist at a specific locus. For example, the gene for eye color might have alleles for blue, brown, or green eyes. Alleles: variants such as alleles for red color
32
Why is gene expression critical to the overall operation of an organism's body?
Gene Expression is the process by which information from a gene is used to synthesize functional gene products (e.g., proteins). This process is critical because: It ensures that the right proteins are produced in the right cells at the right time. It regulates cellular functions, growth, and differentiation. It allows organisms to respond to environmental changes.
33
What is the difference between a molecular function and a trait?
Molecular Function: The specific biochemical activity of a protein or nucleic acid (e.g., enzyme activity, DNA binding). Trait: A characteristic or feature of an organism that is influenced by genes and the environment (e.g., eye color, height).
34
What is the central dogma of molecular biology?
- explains the flow of genetic information within a biological system - DNA -> RNA -> Protein
35
What is a promoter? Why is it essential for RNA transcription?
Promoter: is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter Importance: It is essential for the initiation of RNA transcription as it determines where transcription begins and regulates the gene's expression.
36
What factors are needed for transcription initiation in prokaryotes? In eukaryotes?
Prokaryotes: RNA Polymerase: Enzyme that synthesizes RNA. Sigma Factor: Helps RNA polymerase recognize and bind to the promoter. Eukaryotes: RNA Polymerase II: Enzyme for synthesizing mRNA. General Transcription Factors: Proteins (TFIID, TFIIA, TFIIB, TFIIF, TFIIE, TFIIH) needed for assembling RNA polymerase II at the promoter. Mediator Complex: Assists in assembling RNA polymerase and transcription factors.
37
Contrast eukaryotic and prokaryotic transcription initiation?
Prokaryotic Transcription Initiation: Simpler process with fewer proteins involved. RNA polymerase directly recognizes the promoter with the help of sigma factors. Transcription and translation are coupled; they occur in the cytoplasm. Eukaryotic Transcription Initiation: More complex, involving multiple transcription factors and regulatory elements. RNA polymerase II requires the assembly of general transcription factors and the mediator complex at the promoter. Transcription occurs in the nucleus, and the mRNA is processed before being exported to the cytoplasm for translation.
38
How are eukaryotic RNAs processed? Why is processing necessary prior to translation?
How: Capping, Polyadenylation, splicing Why: Stability, export, accurate coding sequence
39
How does an mRNA triplet (codon) specify an amino acid?
specifies an amino acid by matching with a complementary anticodon on a tRNA molecule during translation (ensures codons corresponds to a specific amino acid following genetic code)
40
What are the three types of RNAs essential for translation? (hint: ribosomes also made up of RNA)
mRNA, tRNA, and rRNA
41
What is necessary for translational initiation?
mRNA, ribosomal subunits, initiator tRNA, initiation factors
42
How are polypeptides elongated during translation?
Codon recognition, peptide bond formation, translocation, repeat
43
How do ribosomes differ between prokaryotes and eukaryotes? Why is this important for the development of antibiotics?
Differ: size (pro smaller, and subunits smaller) Importance: selective targeting, minimized side effects, inhibition of bacterial growth
44
What is a DNA mutation?
is a change in the nucleotide sequence of DNA
45
What are some examples of point mutations? Substitution mutations?
point mutation is a change in a single nucleotide base in the DNA sequence. Insertion Mutations: An additional nucleotide is inserted into the sequence. Deletion Mutations: A nucleotide is removed from the sequence. .Substitution are a specific type of point mutation where one nucleotide in the DNA sequence is replaced with another Silent Mutations: The change does not affect the amino acid produced. Missense Mutations: The change results in a different amino acid being produced.
46
Why is redundancy in the 3rd nucleotide of a codon beneficial?
minimizes the impact of mutations, enhances translational flexibility and efficiency, provides an evolutionary advantage, and allows for the efficient use of tRNAs.
47
How does a frameshift mutation affect translation?
Altered reading frame, premature stop codons, misfolded proteins,
48
Describe the differences between the basic chemical structures of DNA versus RNA nucleotides.
DNA: Deoxyribose (sugar), has thymine, double-stranded RNA: Ribose (sugar), has uracil, single-stranded
49
Understand the direction by which a nucleic acid “grows” (i.e. its directionality).
5' - 3'
50
Describe the secondary structure of a DNA molecule, using terms of “double-helix,” “antiparallel,” and “complementary base pairing.”
secondary structure of DNA is a double-helix composed of two antiparallel strands held together by complementary base pairing
51
Understand which bases form pairs. If given a DNA sequence, be able to identify the complementary strand sequence. If given a DNA sequence: 5'-ATCG-3'
Adenine (A) pairs with Thymine (T) Cytosine (C) pairs with Guanine (G) The complementary strand would be: 3'-TAGC-5'
52
What is a chromosome?
thread-like structure found in the nucleus of eukaryotic cells (and in the cytoplasm of prokaryotic cells) that carries genetic information.
53
What are homologous chromosomes?
are pairs of chromosomes in a diploid organism that have the same length, shape, and genes at the same loci, but they can have different alleles.
54
Describe a nucleosome
nucleosomes are the basic units of DNA packaging, consisting of DNA wrapped around histone proteins
55
What is the difference between euchromatin and heterochromatin?
Euchromatin: Loosely packed, gene-rich, actively transcribed, lighter staining. Heterochromatin: Densely packed, gene-poor, transcriptionally inactive, darker staining.
56
Describe the semiconservative hypotheses about the DNA replication
Concept: Each parental DNA strand serves as a template for a new strand. Outcome: Each new DNA molecule consists of one original strand and one newly synthesized strand. Verification: The Meselson-Stahl experiment confirmed this by showing one old strand and one new strand in replicated DNA. Significance: Ensures accurate genetic information transfer.
57
Describe the functions of the following proteins that play key roles in the process of DNA replication; o DNA polymerase III o DNA helicase o Single-strand binding protein o Topoisomerase o Primase o DNA polymerase I o DNA ligase
DNA Polymerase III Role: Main enzyme for synthesizing new DNA strands. 2. DNA Helicase Role: Unwinds the DNA double helix. 3. Single-Strand Binding Protein (SSB) Role: Stabilizes single-stranded DNA. 4. Topoisomerase Role: Relieves supercoiling tension ahead of the replication fork. 5. Primase Role: Synthesizes RNA primers for DNA polymerase. 6. DNA Polymerase I Role: Replaces RNA primers with DNA. 7. DNA Ligase Role
58
Describe the definitions of the following terms that are relevant to the process of DNA replication; o Origin of replication o Replication bubble o Replication fork o Leading strand o Lagging strand o Okazaki fragment
Origin of Replication Start Site: Genome. Replication Bubble forms when the DNA double helix is unwound at the origin of replication, creating two single-stranded regions flanked by two replication forks. Replication Fork Y-shaped region where the DNA double helix is separated into two single strands that serve as templates for replication Leading Strand is the DNA strand that is synthesized continuously in the same direction as the replication fork movement. Lagging Strand the DNA strand that is synthesized discontinuously in the opposite direction of the replication fork movement (which ends uo forming okazaki) Okazaki Fragment are short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication
59
Explain how the accurate replication is a matter of life and death.
accurate DNA replication is vital for the survival and health of organisms, maintaining genetic stability, ensuring proper cellular function, and preventing diseases.
60
Describe the mechanisms of error detection and correction in DNA replication, proofreading
Proofreading DNA Polymerase: Checks and corrects errors during replication using its exonuclease activity. Mismatch Repair Detection and Repair: Mismatch repair proteins detect errors missed by proofreading, excise the incorrect segment, and resynthesize the correct DNA. Additional Mechanisms Base Excision Repair (BER): Fixes single-base errors. Nucleotide Excision Repair (NER)

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