Genetics and Cell Division: Key Concepts for Biology

What are genes?

Genes are segments of DNA that contain the instructions for building proteins and determining traits.

What is a locus?

A locus is the specific physical location of a gene or other significant sequence on a chromosome.

What are gametes?

Gametes are reproductive cells (sperm and eggs) that carry half the genetic information of an organism.

What is the difference between sexual and asexual reproduction?

Sexual reproduction involves the fusion of gametes from two parents, leading to genetic diversity, while asexual reproduction involves a single organism producing offspring genetically identical to itself.

What is the difference between gametes and somatic cells?

Gametes are reproductive cells that have half the number of chromosomes, while somatic cells are all other body cells that contain the full set of chromosomes.

What are homologous chromosomes?

Homologous chromosomes are pairs of chromosomes that have the same structure and carry genes for the same traits, one inherited from each parent.

What is a karyotype?

A karyotype is a visual representation of an individual's complete set of chromosomes, arranged in pairs and organized by size.

What are sex chromosomes?

Sex chromosomes are the chromosomes that determine the sex of an individual, typically referred to as X and Y in humans.

What are autosomes?

Autosomes are all the chromosomes in an organism that are not sex chromosomes; humans have 22 pairs of autosomes.

What is the difference between haploid and diploid?

Haploid cells contain one complete set of chromosomes (n), while diploid cells contain two complete sets (2n). In humans, gametes are haploid, and somatic cells are diploid.

What does meiosis do?

Meiosis is a type of cell division that reduces the chromosome number by half, producing four genetically diverse haploid gametes.

What are the phases of meiosis?

Meiosis consists of two main phases: Meiosis I (reductional division) and Meiosis II (equational division), each with distinct stages: prophase, metaphase, anaphase, and telophase.

What is synapsis?

Synapsis is the pairing of homologous chromosomes during prophase I of meiosis, allowing for genetic recombination.

What is crossing over?

Crossing over is the exchange of genetic material between homologous chromosomes during synapsis in prophase I of meiosis, increasing genetic diversity.

What are chiasmata?

Chiasmata are the points where homologous chromosomes exchange genetic material during crossing over.

What distinguishes meiosis from mitosis?

Three key events that distinguish meiosis from mitosis are: synapsis and crossing over, the reduction of chromosome number, and the formation of four non-identical gametes.

What are the mechanisms that contribute to genetic variation?

The three mechanisms are: independent assortment of chromosomes, crossing over during meiosis, and random fertilization.

What is the basic structure of DNA?

DNA has a double helix structure composed of two strands of nucleotides, each containing a sugar, phosphate group, and nitrogenous base.

What is the base pairing rule in DNA?

Purines (adenine and guanine) pair with pyrimidines (cytosine and thymine), with two hydrogen bonds between adenine and thymine, and three hydrogen bonds between guanine and cytosine.

What does it mean for DNA strands to be antiparallel?

Antiparallel means that the two strands of DNA run in opposite directions, with one strand oriented 5' to 3' and the other 3' to 5'.

What is the mechanism of DNA replication?

DNA replication is the process by which DNA makes a copy of itself, involving unwinding the double helix, complementary base pairing, and joining new nucleotides.

What is the difference between leading and lagging strand synthesis?

The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized in short segments (Okazaki fragments) away from the fork.

What are Okazaki fragments?

Okazaki fragments are short sequences of DNA synthesized on the lagging strand during DNA replication.

What is helicase?

Helicase is an enzyme that unwinds the DNA double helix during replication.

What is primase?

Primase is an enzyme that synthesizes a short RNA primer to initiate DNA replication.

What is topoisomerase?

Topoisomerase is an enzyme that relieves the tension in the DNA helix ahead of the replication fork by cutting and rejoining the DNA strands.

What are single-stranded DNA binding proteins?

These proteins bind to single-stranded DNA during replication to prevent the strands from re-annealing.

What is DNA polymerase?

DNA polymerase is the enzyme responsible for adding nucleotides to a growing DNA strand during replication.

What is DNA ligase?

DNA ligase is an enzyme that joins Okazaki fragments together on the lagging strand during DNA replication.

What are transcription and translation?

Transcription is the process of synthesizing RNA from a DNA template, while translation is the process of synthesizing proteins from RNA.

What does RNA polymerase do?

RNA polymerase is the enzyme that synthesizes RNA by transcribing the DNA template.

What is a promoter?

A promoter is a DNA sequence that signals the start of a gene and is recognized by RNA polymerase.

What are transcription factors?

Transcription factors are proteins that help regulate the transcription of specific genes by binding to nearby DNA.

What are post-transcriptional modifications?

Post-transcriptional modifications include the addition of a 5' cap, a poly A tail, and splicing to remove introns from the RNA transcript.

What are introns and exons?

Introns are non-coding regions of a gene that are removed during RNA processing, while exons are coding regions that remain in the final mRNA.

What is a codon?

A codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid or stop signal during protein synthesis.

What is a reading frame?

A reading frame is the way nucleotides in mRNA are grouped into codons for translation; shifting the reading frame alters the resulting protein.

What are the basic mechanisms involved in translation?

Translation involves initiation (assembly of ribosome and mRNA), elongation (addition of amino acids), and termination (completion of the polypeptide chain).

What is an anticodon?

An anticodon is a sequence of three nucleotides in tRNA that pairs with a complementary codon in mRNA during translation.

What are the roles of tRNA, rRNA, and mRNA?

tRNA carries amino acids to the ribosome, rRNA is a structural component of ribosomes, and mRNA carries the genetic code from DNA to the ribosome for protein synthesis.

Who is Gregor Mendel?

Gregor Mendel was a scientist known as the father of genetics for his study of inheritance in pea plants, establishing key principles such as the law of segregation and the law of independent assortment.

What is a character in genetics?

A character is a heritable feature that varies among individuals, such as flower color or seed shape.

What is a trait?

A trait is a specific variant of a character, such as purple or white flowers.

What is a true-breeding organism?

A true-breeding organism is one that consistently passes down specific phenotypic traits to its offspring when self-fertilized.

What is a hybrid?

A hybrid is the offspring of two different true-breeding varieties, exhibiting traits from both parents.

What are the P, F1, and F2 generations?

The P generation refers to the parental generation, F1 is the first generation of offspring, and F2 is the second generation resulting from the F1 generation's self-fertilization.

What is the law of segregation?

The law of segregation states that during gamete formation, the two alleles for a trait separate, so each gamete carries only one allele.

What is the law of independent assortment?

The law of independent assortment states that alleles for different traits segregate independently of one another during gamete formation.

What is the difference between dominant and recessive genes?

Dominant genes express their traits even when only one copy is present, while recessive genes only express their traits when two copies are present.

What is the difference between genotype and phenotype?

Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable traits or characteristics.

What is an allele?

An allele is a variant form of a gene that can result in different traits.

What is a Punnett square?

A Punnett square is a diagram used to predict the genetic outcomes of a cross between two organisms, showing the possible combinations of alleles.

What is the difference between homozygous and heterozygous?

Homozygous individuals have two identical alleles for a trait, while heterozygous individuals have two different alleles.

What is a testcross?

A testcross is a breeding experiment used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

What is the difference between a monohybrid and a dihybrid cross?

A monohybrid cross examines the inheritance of a single trait, while a dihybrid cross examines the inheritance of two traits simultaneously.

What is probability in genetics?

Probability in genetics refers to the likelihood of a particular genotype or phenotype occurring, often calculated using the multiplication and addition rules.

What is the multiplication rule?

The multiplication rule states that the probability of two independent events occurring together is the product of their individual probabilities.

What is the addition rule?

The addition rule states that the probability of either of two mutually exclusive events occurring is the sum of their individual probabilities.

What is complete dominance?

Complete dominance occurs when the phenotype of the heterozygote is indistinguishable from that of the homozygous dominant individual.

What is incomplete dominance?

Incomplete dominance occurs when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes.

What is codominance?

Codominance occurs when both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits.

What is pleiotropy?

Pleiotropy is the phenomenon where one gene influences multiple, seemingly unrelated phenotypic traits.

What is polygenic inheritance?

Polygenic inheritance is the inheritance pattern of traits that are controlled by multiple genes, resulting in a continuous range of phenotypes.

What is epistasis?

Epistasis is a genetic interaction where the expression of one gene is affected by one or more other genes.

What is pedigree analysis?

Pedigree analysis is a diagrammatic method used to trace the inheritance of traits through generations in a family.

What is a genetic carrier?

A genetic carrier is an individual who carries one copy of a recessive allele for a trait but does not exhibit the trait themselves.

What is the difference between recessively and dominantly inherited disorders?

Recessively inherited disorders require two copies of the recessive allele to express the disorder, while dominantly inherited disorders require only one copy of the dominant allele.

What are genetic screens at the fetal and newborn level?

Genetic screens are tests performed to identify genetic disorders in fetuses or newborns, often involving blood tests or genetic analysis.