BIOL 1040 Test 5 Study Guide

These flashcards cover key terms and concepts from the BIOL 1040 Test 5 study guide, focusing on topics such as DNA to protein synthesis, cell division, genetics, and inheritance.

Gene Expression

The process by which information from a gene is used to synthesize a functional gene product, typically proteins.

Transcription

The process of copying a segment of DNA into RNA. DNA —> RNA. First step in gene expression. Copies ONE gene, not the entire strand. The double helix is unchanged after. Happens in the nucleus (because it deals with DNA).

Translation

The process of synthesizing a protein from the mRNA template. RNA —> protein. Occurs in the cytoplasm.

Mutation

A change in the DNA sequence that may lead to altered function of genes.

mRNA (messenger RNA)

A type of RNA that carries the genetic information from DNA to the ribosome for protein synthesis.

tRNA (transfer RNA)

A type of RNA that helps decode mRNA into a protein by bringing amino acids to the ribosome.

rRNA (ribosomal RNA)

The type of RNA that, along with proteins, makes up the ribosome.

Codon

A sequence of three nucleotides on mRNA that corresponds to a specific amino acid.

Anticodon

A sequence of three nucleotides on tRNA that is complementary to an mRNA codon.

Chromatid

One half of a duplicated chromosome.

Centromere

The region of a chromosome where the two sister chromatids are joined together.

Cytokinesis

The process by which a single cell divides into two daughter cells after mitosis.

Cancer

A disease characterized by uncontrolled cell division.

Ploidy

The number of sets of chromosomes in a cell, e.g., diploid (2n) or haploid (n).

Homologous Chromosomes

Pairs of chromosomes that have the same structure and gene sequence but may have different alleles.

Genotype

The genetic constitution of an individual, consisting of alleles inherited from parents.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by its genotype.

Random Fertilization

The process by which any sperm can fuse with any egg, contributing to genetic variation.

Down Syndrome

A genetic disorder caused by nondisjunction, resulting in an extra copy of chromosome 21.

compare and contrast structures of dna and rna

• Sugar: DNA has deoxyribose, RNA has ribose.

• Strands: DNA is double-stranded, RNA is single-stranded.

• Bases: DNA uses thymine (T), RNA uses uracil (U) instead.

• Stability: DNA is more stable; RNA is less stable.

• Function: DNA stores genetic info; RNA helps build proteins.

• Location: DNA stays mostly in the nucleus; RNA moves to the cytoplasm.

• Types: DNA has one type; RNA has several types (like mRNA, tRNA, rRNA).

where do transcription and translation occur

Transcription happens in the nucleus – DNA is copied into mRNA.
Translation happens in the cytoplasm – mRNA is used to build proteins at ribosomes.

In prokaryotes, both processes occur in the cytoplasm.

steps of transcription

• Enzyme: RNA polymerase

• Steps:

  1. Initiation: RNA polymerase binds to DNA at the promoter.

  2. Elongation: It builds mRNA by adding RNA nucleotides.

  3. Termination: Transcription ends when a stop signal is reached.

  4. Processing (eukaryotes): mRNA is spliced and capped before leaving the nucleus.

compare and contrast replication and transcription

• Replication makes a full copy of DNA using DNA polymerase.

• Transcription makes an mRNA copy of a gene using RNA polymerase.

• Replication copies both strands; transcription uses one strand.

• Replication uses thymine (T); transcription uses uracil (U) instead.

start codon

"Start here" signal for building a protein

stop codon

"Finish here" signal to stop building the protein

steps of translation and enzyme used

1. Initiation: Ribosome binds to mRNA at the start codon (AUG), and the first tRNA (carrying methionine) attaches.

2. Elongation: Ribosome moves along mRNA, tRNAs bring amino acids, and peptide bonds form between them.

3. Termination: Ribosome reaches a stop codon, releasing the completed protein.

Enzyme used: Peptidyl transferase (catalyzes peptide bond formation).

what is the impact of mutations and how redundancy in the genetic code reduces their impact

Mutations can alter proteins and cause diseases, but the redundancy in the genetic code often helps minimize these effects by allowing some mutations to have no impact on protein function.

cell cycle

• Interphase (where the cell spends most of its time):

  • G1 phase (Gap 1): The cell grows and performs normal functions.

  • S phase (Synthesis): DNA is replicated.

  • G2 phase (Gap 2): The cell continues to grow and prepares for division.

• M Phase (Mitosis): The cell divides into two identical daughter cells.

  • Mitosis (nuclear division): The nucleus divides.

  • Cytokinesis (cytoplasmic division): The cytoplasm divides.

    The cell cycle is the process by which a cell grows, replicates its DNA, and divides into two new cells

mutagen

any agent or substance that causes a change (mutation) in the DNA sequence of an organism

carcinogen

any substance or agent that can cause cancer by inducing changes in the DNA that lead to uncontrolled cell growth

reasons cells divide

• Growth – To increase the number of cells and size of the organism.

• Reproduction – Asexual reproduction in unicellular organisms, and gamete formation in multicellular organisms.

• Repair and Regeneration – To replace damaged or dead cells.

• Maintaining Surface Area-to-Volume Ratio – To optimize material exchange.

• Specialization – To create specialized cells for different functions in the body.

3 phases of cell cycle

• Interphase (includes G1, S, and G2 phases):

  • G1 phase: Cell growth and normal functions.

  • S phase: DNA replication.

  • G2 phase: Preparation for cell division.

• Mitosis (M phase): Division of the nucleus, which includes prophase, metaphase, anaphase, and telophase.

• Cytokinesis: Division of the cytoplasm, resulting in two daughter cells.

3 phases of interphase in order and what occurs

1. G1 Phase (Gap 1):

   • What occurs: The cell grows, performs normal functions, and prepares for DNA replication. It also synthesizes proteins and organelles.

2. S Phase (Synthesis):

   • What occurs: DNA replication happens, where the cell’s entire genome is copied to prepare for cell division.

3. G2 Phase (Gap 2):

   • What occurs: The cell continues to grow and makes final preparations for mitosis, including the production of proteins needed for cell division.

where replication fits into cell cycle and what occurs

DNA replication occurs during the S phase (Synthesis phase) of Interphase in the cell cycle.

What happens during replication in the S phase:

• The DNA in the cell is duplicated to ensure that each daughter cell receives an identical copy of the genome after cell division.

• The DNA double helix unwinds, and each strand serves as a template for creating a new complementary strand.

• DNA polymerase is the main enzyme involved in adding new nucleotides to form the new DNA strand, ensuring accurate replication of the genetic material.

• By the end of the S phase, the cell has two complete sets of DNA (one for each daughter cell).

phases of mitosis in order

• Prophase:

  • The chromatin condenses into visible chromosomes.

  • The nuclear envelope begins to break down.

  • The mitotic spindle starts to form.

• Metaphase:

  • The chromosomes align along the metaphase plate (center of the cell).

  • Spindle fibers attach to the centromere of each chromosome.

• Anaphase:

  • The sister chromatids are pulled apart toward opposite poles of the cell.

  • The centromere splits, and the chromatids move along the spindle fibers.

• Telophase:

  • The chromatids reach the poles, and the nuclear envelope re-forms around each set of chromosomes.

  • Chromosomes begin to de-condense back into chromatin

how does cytokinesis occur in plants vs. animals

Cytokinesis in Animal Cells:

• Process: Cleavage furrow forms.

• A contractile ring made of actin filaments pinches the cell membrane in the middle, forming a cleavage furrow that deepens until the cell is divided into two daughter cells.

• This physical pinching process results in two separate, independent cells.

  Cytokinesis in Plant Cells:

  • Process: Cell plate formation.

  • In plant cells, a cell plate forms at the center, where the cell wall will eventually be.

  • Vesicles filled with cellulose and other materials fuse to form the cell plate.

  • The cell plate grows outward until it fuses with the cell membrane, creating two daughter cells, each surrounded by a new cell wall.

why cell cycle checkpoints are important for the cell

Cell cycle checkpoints are like quality control systems. They ensure:

• DNA integrity is maintained.

• The cell doesn't divide with errors.

• Repairs are made when needed.

• The cell only divides when it's ready, avoiding uncontrolled division (like cancer)

state possible causes of cancer

Cancer can be caused by genetic mutations, exposure to carcinogens, lifestyle factors (like diet and exercise), hormonal imbalances, aging, and immune system issues

explain the relationship between cell cycle regulation and cancer

Cancer occurs when cell cycle regulation is disrupted. This can happen when:

• Tumor suppressor genes (e.g., p53) fail to stop the cycle in response to damage.

• Oncogenes become overactive, pushing the cell cycle forward uncontrollably.

• Cell cycle checkpoints fail, allowing errors in DNA replication and chromosome segregation to pass unchecked.

Uncontrolled cell division due to these disruptions leads to the formation of tumors and the development of cancer.

Explain the normal function and the mutated function of proto-oncogenes and tumor suppressor genes

• Proto-oncogenes normally help cells grow and divide. When mutated, they become oncogenes and cause uncontrolled cell division (like a stuck gas pedal).

• Tumor suppressor genes normally slow down cell division, repair DNA, or trigger cell death. When mutated, they lose control, allowing damaged cells to keep dividing (like failed brakes).

Explain the role of mutations in causing cancer

Mutations can cause cancer by damaging genes that control the cell cycle. They may:

• Turn proto-oncogenes into oncogenes (too much cell growth),

• Inactivate tumor suppressor genes (no cell cycle control),

• Prevent DNA repair (more mutations build up).

This leads to uncontrolled cell division and tumor formation

determine the effect of a mutation on the protein produced by the mutated gene

A mutation changes the DNA → which changes the mRNA → which can change the amino acid sequence → which can alter or disrupt the protein’s function

diploid

a cell that contains two complete sets of chromosomes, one from each parent

haploid

a cell that contains only one set of chromosomes — half the number found in diploid cells

gamete

a reproductive cell that contains half the number of chromosomes (haploid, n) and is used in sexual reproduction

dominant trait

a trait that is expressed in an organism even if only one copy of the gene (allele) is present (A)

recessive trait

a trait that is only expressed when both copies of the gene (alleles) are recessive (a)

homozygous

having two identical alleles for a particular gene, one inherited from each parent (AA or aa)

heterozygous

having two different alleles for a particular gene, one inherited from each parent (Aa)

phenotype

observable characteristics or traits of an organism, which result from the interaction of its genotype (genetic makeup) with the environment

genotype

genetic makeup of an organism — the specific set of alleles (versions of a gene) that it carries

gene

a segment of DNA that contains the instructions for making a specific protein or function in the body, which in turn influences an organism's traits

allele

a different version of a gene. Each gene can have several variations (alleles) that affect an organism's characteristics

carrier

an individual who carries one copy of a recessive allele for a particular trait or genetic disorder but does not display the trait or disorder themselves because the dominant allele masks it

homologous chromosomes

pairs of chromosomes that have the same structure and carry the same genes, but possibly with different versions (alleles) of those genes. One chromosome in each pair is inherited from the mother, and the other is inherited from the father

autosomes

non-sex chromosomes that are the same in both males and females. They carry the majority of an organism's genetic information, excluding those related to sex determination

random fertilization

the process by which any sperm can fertilize any egg, resulting in a wide variety of genetic combinations in offspring

Describe the genetic basis for the disorder cystic fibrosis

Cystic fibrosis is caused by a recessive mutation in the CFTR gene, where individuals with two mutated alleles (homozygous recessive, cftr/cftr) produce a nonfunctional CFTR protein. This results in the buildup of thick mucus that affects the lungs and digestive system.

Use appropriate terminology to describe the chromosomes found in cells

• Body cells are diploid (2n), containing 23 pairs of chromosomes (22 autosomes + 2 sex chromosomes), making a total of 46 chromosomes.

• Gametes are haploid (n), containing only one set of chromosomes (23 chromosomes in total, including one sex chromosome).

This division is crucial for sexual reproduction, as the fusion of two haploid gametes during fertilization restores the diploid number in the zygote.

State the roles of the processes of mitosis, meiosis, and fertilization in sexual reproduction

• Mitosis: Allows growth, development, and repair of tissues by creating identical cells.

• Meiosis: Produces haploid gametes with half the chromosome number to ensure genetic diversity and the proper chromosome number after fertilization.

• Fertilization: Combines genetic material from two parents to form a diploid zygote, ensuring genetic diversity and the continuation of the species

Describe the cell “cycle” for cells undergoing meiosis

1. Interphase (G1, S, G2) — Preparation and DNA replication.

2. Meiosis I (Prophase I, Metaphase I, Anaphase I, Telophase I) — Reduces chromosome number by half.

3. Interkinesis (optional, no DNA replication).

4. Meiosis II (Prophase II, Metaphase II, Anaphase II, Telophase II) — Separation of sister chromatids into four haploid cells.

Explain the key events in meiosis which transform one diploid cell into four haploid cells

Meiosis I:

• Purpose: Reduces chromosome number by half.

• Key Events:

  • Prophase I: Homologous chromosomes pair and exchange genetic material (crossing over).

  • Metaphase I: Tetrads (paired homologous chromosomes) align at the cell's center.

  • Anaphase I: Homologous chromosomes are pulled to opposite poles.

  • Telophase I & Cytokinesis: Two haploid cells are formed.

Meiosis II:

• Purpose: Separates sister chromatids, like mitosis.

• Key Events:

  • Prophase II: Chromosomes condense and spindle fibers form.

  • Metaphase II: Chromosomes align at the center.

  • Anaphase II: Sister chromatids are separated.

  • Telophase II & Cytokinesis: Four genetically diverse haploid cells are produced.

The result is four haploid cells, each with half the chromosome number, contributing to genetic diversity through crossing over and independent assortment.

State and explain the key events in Meiosis I that make it unique

1. Pairing of Homologous Chromosomes (Synapsis): Homologous chromosomes pair up to form tetrads, enabling genetic recombination.

2. Recombination (Crossing Over): Chromatids from homologous chromosomes exchange genetic material, creating new allele combinations.

3. Independent Assortment: Homologous chromosomes align randomly during Metaphase I, resulting in the random distribution of chromosomes to gametes.

These events in Meiosis I ensure that the resulting gametes are genetically diverse, which is essential for the variation seen in sexually reproducing populations

Compare and contrast mitosis and meiosis

• Mitosis: One division, no genetic variation, results in two diploid cells.

• Meiosis: Two divisions, genetic variation, results in four haploid cells.

Describe the events in sexual reproduction which contribute to genetic variation in offspring

Genetic variation in offspring is driven by:

• Crossing over during meiosis, which reshuffles genetic material between homologous chromosomes.

• Independent assortment, which randomly distributes chromosomes into gametes.

• Random fertilization, where any sperm can fertilize any egg, creating countless possible genetic combinations.

Explain why genetic variation is important for a population (natural selection)

Genetic variation is crucial for a population because it allows for adaptability to environmental changes. It provides the raw material for natural selection, enabling individuals with beneficial traits to survive and reproduce, passing on those traits. This diversity helps populations avoid inbreeding depression, promote evolutionary change, and ensures long-term survival by making them more resilient to diseases or environmental shifts. Without genetic variation, a population would struggle to adapt, increasing the risk of extinction.

Explain the difference between paternal/identical and fraternal twins

• Identical twins: One egg and one sperm, genetically identical.

• Fraternal twins: Two eggs and two sperm, genetically like regular siblings.

Explain the disorder Down Syndrome and its genetic basis (nondisjunction)

Down syndrome (trisomy 21) is a genetic disorder caused by an extra copy of chromosome 21. It typically results from nondisjunction during meiosis, where chromosomes fail to separate properly, leading to a gamete with an extra chromosome. When this gamete fuses with a normal one, the child inherits three copies of chromosome 21. Symptoms include physical features like a flattened face and developmental delays. There are also increased risks for health issues, such as heart defects