Cell Division, DNA Replication, and Genetic Engineering

Interphase

Period before mitosis begins where the cell grows, replicates DNA, and prepares for division

Telophase I

Two haploid daughter cells are formed

Metaphase II

Chromosomes align along metaphase plate in each haploid cell

Recombination

Process where genetic material from two homologous chromosomes is exchanged during meiosis

Alleles

Different versions of a gene

Mitosis

Type of cell division that results in two genetically identical daughter cells

Metaphase

Condensed chromosomes line up along the cell's equator, spindle fibers attach

Cytokinesis

Division of cell's cytoplasm and organelles

Metaphase I

Homologous chromosome pairs line up along metaphase plate

Anaphase I

Homologous chromosomes separate and move to opposite poles

Prophase II

Chromosomes condense, new spindle apparatus forms in each haploid cell

Mitosis

Somatic cell division for growth and repair

Sister Chromatids

Identical copies of a chromosome produced during DNA replication

F1 Generation

Offspring of the P generation

Phenotypic Ratio

Ratio of different phenotypes in a cross

Dihybrid Cross

Cross involving two traits that assort independently

Blood Types

Type O is universal donor, type AB is universal receiver

Trisomy

One extra chromosome (2n+1)

Base Pairs Bound by Hydrogen Bonds

Complementary base pairs

Leading Strand

Synthesized continuously in the direction of replication fork

Anticodons

Complementary sequences to codons on tRNA molecules

Exons

Regions of a gene that code for amino acids

Adenovirus

Virus used in gene therapy, can provoke immune response

Dolly

First cloned mammal (sheep)

Genetically Modified Crops

Crops with improved traits through genetic engineering

Genetic Engineering in Livestock

Production of livestock with desired traits through genetic engineering

Heterozygous

Individuals with two different alleles for a particular gene

Phenotype

Physical expression of genotype

Prophase

Chromatin condenses into visible chromosomes, nuclear envelope breaks down, spindle fibers form

Anaphase

Sister chromatids are pulled apart by spindle fibers towards opposite poles

Telophase

Separated chromatids arrive at opposite poles, nuclear envelope re-forms

Meiosis

Specialized cell division process that produces gametes in sexually reproducing organisms

Prophase I

Homologous chromosomes pair up, may exchange genetic material

Anaphase II

Sister chromatids separate and move to opposite poles in each haploid cell

Telophase II

Four haploid daughter cells are produced

G1

Cell growth and normal function

S

DNA replication occurs

G2

Further growth and preparation for cell division

Meiosis

Germ cell division for production of gametes

G1 Checkpoint

Control point in cell cycle where cell assesses readiness to proceed

G2 Checkpoint

Control point in cell cycle where cell assesses readiness for mitosis

M Checkpoint

Control point in cell cycle where cell ensures chromosomes are properly aligned

Homologous Recombination

Exchange of genetic material between homologous chromosomes

Meiosis Errors

Errors in meiosis can result in aneuploidy or non-disjunction

Heredity

Passing of traits from one generation to the next through genetic inheritance

P Generation

Initial generation in a breeding experiment

F2 Generation

Offspring of the F1 generation

Dominant Traits

Expressed when even one copy of dominant allele is present

Recessive Traits

Expressed only when two copies of recessive allele are present

Genes

Segments of DNA that contain instructions for specific traits

Trait

Physical or genetic characteristic determined by alleles

Homozygous

Individuals with two identical alleles for a particular gene

Genotype

Organism's genetic makeup

Mendel's Laws

Law of Segregation and Law of Independent Assortment

Genes on Same Chromosome

Genes close together on same chromosome tend to be inherited together

Continuous Variation

Traits with wide range of phenotypes influenced by multiple genes

Pleiotropic Effects

One gene affects multiple traits

Incomplete Dominance

Blending of traits

Codominance

Simultaneous expression of both alleles

Sex Chromosomes

XY represents a male

Monosomy

One less chromosome (2n-1)

Non-Disjunction of X Chromosome

Can result in Turner syndrome (XO) or Klinefelter syndrome (XXY)

Bases in Nucleotides

Purines (adenine and guanine) and pyrimidines (thymine, cytosine, and uracil in RNA)

Base Pairing in DNA

Adenine pairs with thymine, guanine pairs with cytosine

DNA Form in Eukaryotes

Double helix

Semi-Conservative DNA Replication

Each newly formed DNA molecule consists of one original and one newly synthesized strand

Enzymes in DNA Replication

DNA helicase, DNA polymerase, RNA primase, DNA ligase

DNA Replication Steps

Initiation, Unwinding, Single-Strand Binding Proteins, Primer Synthesis, DNA Synthesis, Proofreading and Repair, Termination, Telomeres, Completion

Lagging Strand

Synthesized in short fragments (Okazaki fragments)

Central Dogma

Flow of genetic information: Transcription and Translation

Transcription

Synthesis of complementary RNA molecule based on DNA template

Translation

Assembly of amino acids into polypeptide chain based on mRNA template

mRNA (messenger)

Carries genetic information from DNA to ribosome where it serves as a template for protein synthesis during translation. Contains Codons

tRNA (transfer)

Brings specific amino acids to ribosome during translation. Each of these have an anticodon

rRNA (ribosomal)

Structural component of ribosomes (where translation takes place)

Codons

Three-nucleotide sequences in mRNA that code for amino acids

Introns

Non-coding regions within a gene

Mutation

Changes in DNA sequence

Genome

Complete set of an organism's genetic material

Chromosomes

Structures within cells that contain DNA

Genes

Specific segments of DNA that encode instructions for making proteins or functional RNA molecules

Alleles

Different versions of a gene

Genetic Engineering

Manipulation of an organism's genetic material

Restriction Enzymes

Enzymes used to cut DNA at specific sequences. create sticky ends that can be joined to other DNA fragments with complementary ends

Adeno-Associated Virus

Virus used in gene therapy, less immunogenic than adenovirus

Embryonic Stem Cells

Derived from early-stage embryos, totipotent, used in regenerative medicine

Therapeutic Cloning

Creating an embryo with same genetic material as a patient for medical purposes

Reproductive Cloning

Creating a genetically identical organism

Genomic Imprinting

Certain genes expressed in parent-of-origin-specific manner

Genetic Engineering in Medicine

Development of recombinant DNA technology, gene therapy, production of therapeutic proteins

DNA Replication

This process by which a DNA molecule is replicated to produce two identical copies. It occurs during the S phase of the cell cycle and involves the unwinding of the double helix, separation of the DNA strands, and the synthesis of new complementary strands using the existing strands as templates.

1. Initiation in DNA Replication

The first stage of DNA replication where the double helix unwinds and separates into two strands. Enzymes, such as helicase, break the hydrogen bonds between the base pairs, forming a replication fork. DNA polymerase then binds to the separated strands, initiating the synthesis of new DNA strands.

2. Unwinding in DNA Replication

Process where DNA strands separate and unwind to expose the nucleotide bases for replication. Enzyme helicase breaks hydrogen bonds between base pairs, creating a replication fork.

3. Single-Strand Binding Proteins in DNA Replication

Proteins that stabilize and protect single-stranded DNA during DNA replication. They prevent the reannealing of the separated DNA strands and facilitate the binding of other enzymes involved in replication.

4. Primer Synthesis In DNA Replication

The process of creating short RNA primers by the enzyme primase during DNA replication. Primers provide the starting point for DNA polymerase to begin synthesizing new DNA strands. They are complementary to the template DNA strand and serve as a primer for DNA synthesis.

5. DNA Synthesis in DNA Replication

Process where new DNA strands are synthesized using existing strands as templates. It occurs during the S phase of the cell cycle and involves DNA polymerase enzyme adding complementary nucleotides to the template strands. Two new DNA molecules are formed, each with one original and one newly synthesized strand.

6. Proofreading and Repair in DNA Replication

Process that occurs during DNA replication to correct errors in the newly synthesized DNA strand. DNA polymerase proofreads the strand for mistakes and repairs them by removing the incorrect nucleotide and replacing it with the correct one. Ensures accuracy and fidelity in DNA replication.

7. Termination in DNA Replication

The final stage of DNA replication where the replication process stops. It occurs when the DNA polymerase reaches the end of the DNA strand or encounters a termination signal. Termination ensures that the entire DNA molecule is replicated accurately.

8. Telomeres in DNA Replication

Protective structures at the ends of chromosomes that prevent the loss of genetic material during DNA replication. They shorten with each cell division, influencing the aging process and lifespan of cells.

9. Completion in DNA Replication

The process where DNA polymerase adds nucleotides to the growing DNA strand, following the template strand, until it reaches the end of the DNA molecule.