Unit 3 Biology

Haploid

A cell with half of a set of chromosomes with one pair of each chromosome making 23 chromosomes

Diploid

A cell with a complete set of chromosomes (46), one pair of chromosmes form each parent

Gamete

A haploid reproductive cell (sperm or egg) that merges with another gamete during fertilization to form a diploid zygote.

Zygote

A fertilized egg formed by the union of two gametes, containing a diploid set of chromosomes.

F1 generation

The first filial generation of offspring produced from a cross between two parental (P) organisms, typically exhibiting traits inherited from both parents.

P generation

The parental generation in a genetic cross, consisting of the original organisms that are crossed to produce the F1 generation.

F2 generation

The second filial generation of offspring produced by crossing individuals from the F1 generation, which may exhibit a variety of traits due to genetic recombination and segregation.

Gene

A segment of DNA that contains the instructions for building a specific protein or RNA molecule, which determines a particular trait or characteristic in an organism.

Allele

A variant form of a gene that can result in different traits; individuals inherit two alleles for each gene, one from each parent.

Genotype

The genetic makeup of an organism, specifically the combination of alleles for a particular gene or set of genes.

Phenotype

The observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment.

Homozygous

An organism that has two identical alleles for a specific gene, either both dominant or both recessive.

Heterozygous

An organism that has two different alleles for a specific gene, one dominant and one recessive.

Dominant Allele

An allele that expresses its trait or phenotype in the presence of another allele; it masks the effect of the recessive allele when both are present in a heterozygous individual.

Recessive Allele

An allele that only expresses its trait or phenotype when two copies are present (homozygous condition); it is masked by a dominant allele in a heterozygous individual.

Phenotype Plasticity

The ability of an organism to change its phenotype in response to environmental conditions, allowing it to adapt to varying environments or situations.

Gene Expression

The process by which information from a gene is used to synthesize a functional gene product, typically a protein or RNA, influencing an organism's traits and functions.

phenylketonuria

A genetic disorder resulting from a deficiency in the enzyme phenylalanine hydroxylase, leading to phenylalanine buildup, which can cause intellectual disability if untreated.

Gene pool

The total set of genetic information and alleles present in a population, encompassing all the genes and their variants within that group.

Base subsituion mutation

A genetic mutation where one nucleotide is replaced by another, potentially altering the amino acid sequence of a protein.

Single nucleotide polymorphism

A variation at a single nucleotide position in a DNA sequence among individuals, which can influence traits and susceptibility to diseases.

Multiple Alleles

A genetic scenario where a gene has more than two alternative forms (alleles) in a population, leading to a variety of possible phenotypes.

ABO blood groups

A system of classifying human blood based on the presence or absence of antigens A and B on the surface of red blood cells, resulting in four main blood types: A, B, AB, and O.

Incomplete dominance

A genetic situation where neither allele is completely dominant, resulting in a heterozygous phenotype that is a blend of the two parental traits.

Codominance

A genetic scenario in which both alleles in a heterozygous individual are fully expressed, resulting in a phenotype that displays both traits simultaneously.

Autosomes

Chromosomes that are not involved in determining the sex of an organism; in humans, there are 22 pairs of autosomes, numbered 1 through 22.

Haemophilia

A genetic disorder that impairs the body's ability to make blood clots due to a deficiency in specific clotting factors, leading to excessive bleeding. It is typically inherited in an X-linked recessive pattern.

Sex-Linked Trait

A trait determined by a gene located on a sex chromosome (typically the X chromosome), leading to different patterns of inheritance in males and females.

Pedigree

A diagram that represents the genetic relationships and inheritance patterns within a family, often used to track the transmission of specific traits or genetic disorders across generations.

Polygeneic inheritacne

A form of inheritance in which multiple genes (often located on different chromosomes) contribute to a single trait, resulting in a continuous range of phenotypes.

continuos variation

A type of genetic variation in which a trait exhibits a range of phenotypes, rather than distinct categories, often influenced by multiple genes and environmental factors. Examples include height and skin color.

discrete variation

A type of genetic variation where traits are categorized into distinct groups or categories, with no intermediates. Examples include blood types and flower color (e.g., red or white).

melanin

A pigment produced by melanocytes in the skin, hair, and eyes that gives color and protects against UV radiation; it plays a key role in determining an individual's skin tone.

DNA

The molecule that carries genetic information in living organisms, composed of two strands forming a double helix, made up of nucleotides containing the bases adenine (A), thymine (T), cytosine (C), and guanine (G).

Nucelotide

The basic building block of DNA and RNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine in DNA; uracil replaces thymine in RNA).

Dna replication

The biological process by which a cell makes an identical copy of its DNA, resulting in two double helices, each containing one original and one newly synthesized strand. This occurs during the S phase of the cell cycle and involves enzymes like DNA polymerase.

Helicase

An enzyme that unwinds and separates the double-stranded DNA during replication, allowing the strands to be copied.

complementary base pairs

Pairs of nucleotide bases that bond together in DNA and RNA; in DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). In RNA, adenine pairs with uracil (U) instead of thymine.

semi conserative

A method of DNA replication in which each new double helix consists of one original (parental) strand and one newly synthesized strand, ensuring that genetic information is conserved while being copied.

taq polymerase

heat-stable DNA polymerase enzyme derived from the bacterium Thermus aquaticus, commonly used in polymerase chain reaction (PCR) to amplify DNA because it can withstand the high temperatures required for denaturing DNA strands.

denaturation

The process of heating a double-stranded DNA molecule to separate it into two single strands, typically achieved during PCR, which allows access for primers and DNA polymerase during replication or amplification.

annealing

The process in which single-stranded DNA primers bind to complementary sequences on the template DNA during PCR, allowing the formation of double-stranded DNA at a lower temperature following denaturation.

gel electrophoresis

A laboratory technique used to separate DNA, RNA, or proteins based on their size and charge by applying an electric field to a gel matrix, allowing molecules to migrate through the gel and form distinct bands for analysis.

Dna profile

A unique representation of an individual's DNA characteristics, typically created by analyzing specific regions of the genome, used for identification in forensic science, paternity testing, and genetic research.

restriciton endonuclease

An enzyme that cuts DNA at specific recognition sites, producing fragments with defined lengths and ends, which is widely used in molecular biology for cloning, DNA analysis, and genetic engineering.

DNA primase

An enzyme that synthesizes short RNA primers during DNA replication, providing a starting point for DNA polymerase to begin synthesizing the new DNA strand.

RNA primer

A short strand of RNA synthesized by primase that serves as a starting point for DNA synthesis during replication, allowing DNA polymerase to add DNA nucleotides to the 3' end.

DNA polymerase III

The primary enzyme involved in DNA replication in prokaryotes, responsible for synthesizing new DNA strands by adding nucleotides to the growing chain in a 5' to 3' direction, also possessing proofreading activity to ensure accuracy.

Dna polymerase I

An enzyme involved in DNA replication in prokaryotes that primarily removes RNA primers from newly synthesized DNA strands and fills in the gaps with DNA nucleotides, also possessing proofreading abilities to ensure accuracy.

DNA ligase

An enzyme that joins together DNA fragments by forming covalent bonds between the sugar-phosphate backbones, playing a crucial role in sealing nicks and gaps during DNA replication and repair processes.

gyrase

An enzyme, specifically a type of topoisomerase, that relieves the strain generated ahead of the replication fork by introducing negative supercoils into DNA, helping to prevent tangling and allowing smoother replication.

repliaiton fork

The Y-shaped structure that forms when DNA is unwound during replication, where the two strands separate to allow the synthesis of new complementary strands.

leading strand

The continuously synthesized DNA strand that is formed in the same direction as the movement of the replication fork during DNA replication, allowing for uninterrupted synthesis as nucleotides are added in a 5' to 3' direction.

lagging strand

The discontinuously synthesized DNA strand that is formed in the opposite direction of the replication fork during DNA replication, consisting of short segments called Okazaki fragments, which are later joined together.

continuos replication

The process of DNA synthesis on the leading strand during replication, where nucleotides are added continuously in the 5' to 3' direction without interruptions.

discontinuos replication

The process of DNA synthesis on the lagging strand during replication, where nucleotides are added in short segments (Okazaki fragments) because the DNA is synthesized in the opposite direction to the movement of the replication fork.

okazaki fragments

Short segments of DNA synthesized on the lagging strand during DNA replication, created because the strand is synthesized discontinuously in the direction opposite to the replication fork. These fragments are later joined together by DNA ligase.

dna proofreading

The process by which DNA polymerases check and correct errors during DNA replication. They remove incorrectly paired nucleotides and replace them with the correct ones, enhancing the accuracy of DNA synthesis.

Parent Cell

original cell that divides to form two or more daughter cells in cell division.

Daughter cell

a cell formed from the division of a parent cell during mitosis or meiosis.

Cytokinesis

The division of cytoplasm that completes cell division, forming two separate cells

Cleavage furrow

the indentation that forms during cytokinesis in animal cells, leading to the division into two daughter cells.

cell plate

a structure that forms during cytokinesis in plant cells, eventually developing into a new cell wall between daughter cells.

OOgenesis

is the process of egg cell (ovum) formation in females, involving cell division and maturation in the ovaries.

Budding (in yeast)

Asexual reproduction where a small outgrowth forms on the parent cell, developing into a new cell.

Mitosis

The process of cell division that results in two genetically identical daughter cells, involving phases like prophase, metaphase, anaphase, and telophase.

Meiosis

A type of cell division that reduces the chromosome number by half, producing four genetically diverse haploid cells, essential for sexual reproduction.

Anucleate Cell

A cell that lacks a nucleus, such as a mature red blood cell.

Chromosme

A thread-like structure composed of DNA and proteins, carrying genetic information, found in the nucleus of eukaryotic cells or the cytoplasm of prokaryotes.

Sister Chromatid

Identical copies of a chromosome, formed during DNA replication, that are joined together at the centromere before cell division.

Condenstatin of chromomsomes

The process where chromatin fibers coil and compact into visible chromosomes during cell division, making them easier to separate.

MicroTubules

Hollow, tube-like structures made of protein that provide support, shape, and help with cell division by forming the spindle fibers.

Microtubule motors

Proteins that use energy to move along microtubules, transporting cellular cargo and facilitating processes like cell division and intracellular movement.

Histone protein

Proteins around which DNA winds, helping to package it into a compact structure and playing a role in gene regulation.

Spindle fibers

Protein fibers that form the mitotic spindle during cell division, helping to separate chromosomes by attaching to centromeres and pulling them apart.

Prophase

The first phase of mitosis, where chromosomes condense, the nuclear membrane breaks down, and spindle fibers begin to form.

Metaphase

The second phase of mitosis, where chromosomes align at the cell's equator, attached to spindle fibers at their centromeres.

Anaphase

The third phase of mitosis, where sister chromatids are pulled apart toward opposite poles of the cell.

Telophase

The final phase of mitosis, where chromosomes de-condense, the nuclear membrane re-forms, and two distinct nuclei are created.

Reduction Division

The type of cell division, such as meiosis, that reduces the chromosome number by half, producing haploid cells from a diploid parent.

Prophase I

The first phase of meiosis I, where chromosomes condense, homologous chromosomes pair up, and crossing over occurs, increasing genetic diversity.

Metaphase I

The phase of meiosis I where homologous chromosome pairs align at the cell's equator, preparing for separation into different cells.

Anaphase I

The phase of meiosis I where homologous chromosomes are pulled to opposite poles of the cell, reducing chromosome number by half.

Telophase I

The phase of meiosis I where homologous chromosomes are pulled to opposite poles of the cell, reducing chromosome number by half.

Homologous Chromosomes

Chromosome pairs, one from each parent, that are similar in size, shape, and genetic content, but may carry different alleles.

Bivalent

A pair of homologous chromosomes connected during meiosis I, consisting of four chromatids (two from each chromosome) and forming a tetrad.

Crossing over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis, increasing genetic diversity.

Non-Disjunction

The failure of chromosomes or chromatids to separate properly during meiosis, leading to an abnormal number of chromosomes in the resulting cells.

Down syndrome (trisomy 21)

A genetic disorder caused by the presence of an extra copy of chromosome 21, leading to intellectual disability, characteristic facial features, and potential health issues.

Indpendent Assortment of Chromosmes

The random distribution of homologous chromosomes into gametes during meiosis, contributing to genetic diversity in offspring.

Kinetochores

Protein complexes located at the centromere of chromosomes, where spindle fibers attach during cell division to help separate sister chromatids.

Cell proliferation

The process of rapid cell division and growth, leading to an increase in cell number.

Meristem

A region of plant tissue where cells actively divide, allowing for growth in length (apical meristem) or width (lateral meristem).

Interphase

The phase of the cell cycle where the cell grows, replicates its DNA, and prepares for division, consisting of G1, S, and G2 phases.

G1 phase

The first phase of interphase, where the cell grows, synthesizes proteins, and carries out normal functions before DNA replication.

s phase

The phase of interphase where DNA is replicated, ensuring that each daughter cell will have an identical set of chromosomes after division.

g2 phase

The second growth phase of interphase, where the cell continues to grow, produce proteins, and prepare for cell division by checking DNA replication.

cyclins

Proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs), controlling progression through different phases of cell division.

cyclin dependent kinases

Enzymes activated by cyclins that regulate the progression of the cell cycle by phosphorylating target proteins, driving the cell through checkpoints.

tumoru suppressor gene

A gene that helps regulate cell growth by preventing uncontrolled cell division. When mutated, it can lead to cancer development.