Mod 5 Flashcards
Define diploid cell.
A diploid cell has two complete sets of chromosomes, with one chromosome inherited from each parent (e.g., human cells have 23 pairs of chromosomes).
Define somatic cell.
A somatic cell is any cell of a living organism other than the reproductive cells, having 46 chromosomes (23 pairs) and is diploid.
What is mitosis?
Mitosis is a type of cell division that somatic cells undergo, resulting in daughter cells that are genetically identical to the original cell.
What is the role of mitosis?
The role of mitosis includes growth of multicellular organisms, maintenance and repair, asexual reproduction, and genetic stability.
What is the cell cycle?
The cell cycle is a series of events that take place in a cell as it grows and divides, spending most of its time in interphase.
Define interphase.
Interphase is the preparation phase before a cell divides, subdivided into G1, S, and G2 stages.
What happens during G1 phase?
In the G1 phase, cellular contents excluding the chromosomes are duplicated, and cells increase in size.
What happens during S phase?
In the S phase, each of the 46 chromosomes is duplicated, resulting in 92 chromatids, as DNA replicates and becomes double-stranded.
Define chromatid.
A chromatid is one of the two identical halves of a chromosome that has been replicated in preparation for cell division.
What is the function of the centromere?
The centromere is a constricted region of a chromosome that connects sister chromatids.
What occurs during G2 phase?
During the G2 phase, the cell checks the duplicated chromosomes for errors and makes any needed repairs.
What is G0 phase?
The G0 phase is a resting phase where the cell is neither dividing nor preparing to divide, performing maintenance and other functions.
Describe prophase in mitosis.
In prophase, chromosomes condense and become visible as two identical strands, the nuclear membrane breaks down, and centrioles move to opposite ends, forming spindle fibers.
What happens in metaphase?
In metaphase, chromosomes line up in a single file at the center of the cell, and spindle fibers attach to their centromeres.
What occurs during anaphase?
In anaphase, spindle fibers shorten and pull apart the sister chromatids towards opposite poles, causing the cell to elongate.
Describe telophase in mitosis.
In telophase, spindle fibers dissolve, new nuclear membranes regenerate around daughter chromosomes, and a furrow forms, pinching the cell into two.
Define cytokinesis.
Cytokinesis is the physical process of cell division that divides the cytoplasm of the parental cell into two daughter cells.
How does cytokinesis differ in plant and animal cells?
In plant cells, cytokinesis is centrifugal, starting at the center, while in animal cells, it is centripetal, starting at the edges.
What is meiosis?
Meiosis is a type of cell division that produces gametes with a haploid number of chromosomes, resulting in four daughter cells that are not identical to parent cells.
Define haploid.
Haploid refers to the presence of a single set of chromosomes in an organism’s cells.
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes of the same length and centromere position, one inherited from the mother and one from the father.
What is crossing over?
Crossing over occurs during the formation of tetrads when homologous chromosomes align, exchanging genetic information, leading to genetic variation.
What happens during prophase I of meiosis?
In prophase I, chromosomes condense, the nuclear membrane disappears, and homologous chromosomes undergo synapsis and crossing over.
Describe metaphase I in meiosis.
In metaphase I, pairs of homologous chromosomes line up at the equator in tetrads, with one chromatid facing each pole.
What occurs during anaphase I?
In anaphase I, chromosomes move towards either pole, with sister chromatids remaining attached at the centromere, resulting in independent assortment.
Describe telophase I and cytokinesis in meiosis.
Each half of the cell has a haploid set with two sister chromatids, the spindle disappears, and cytokinesis occurs, forming two haploid cells.
What happens during prophase II?
In prophase II, the nuclear membrane disintegrates again, and a spindle apparatus forms at right angles to the previous spindle.
What occurs during metaphase II?
In metaphase II, sister chromatids line up at the equator, attaching to spindle fibers in a single file.
Describe anaphase II.
In anaphase II, centromeres separate, and sister chromatids are pulled apart to opposite poles, each now considered an individual daughter chromosome.
What happens during telophase II and cytokinesis?
In telophase II, chromosomes reach poles, the spindle disappears, nuclei regenerate, and cytokinesis produces four daughter cells, each with half the number of chromosomes.
Define linked genes.
Linked genes are genes located close together on the same chromosome, usually inherited together.
What are chromosomes?
Chromosomes are thread-like structures found in the nucleus, carrying genetic information in the form of genes, made of 40% DNA and 60% protein.
What are genes?
Genes are small lengths of DNA that encode for specific traits that can be passed from parent to offspring.
Define locus.
A locus is the position of a gene on a chromosome.
What are peptides
Peptides are short chains of amino acids linked by peptide bonds.
What is a polypeptide?
A polypeptide is a longer, continuous, unbranched peptide chain, and one or more folded polypeptides form a protein.
What is the structure of DNA?
DNA is a double helix made of two strands held together by weak hydrogen bonds, consisting of nucleotides made up of a phosphate group, a sugar group, and nitrogenous bases.
What are the differences between DNA and RNA?
RNA exists as single strands, has ribose sugar instead of deoxyribose, and contains uracil instead of thymine. It has three forms: mRNA, rRNA, and tRNA.
What is DNA replication?
DNA replication is the production of two identical double-stranded molecules of DNA from one original double helix, occurring during interphase.
What is the role of helicase in DNA replication?
Helicase unwinds the DNA helix, breaking weak hydrogen bonds and exposing nucleotide bases, forming the replication fork.
What are RNA primers?
RNA primers are made by primase and act as markers for where DNA polymerase begins synthesis on the existing DNA template.
What does DNA Polymerase III do?
DNA Polymerase III adds nucleotides to the growing DNA chain, synthesizing the new strand in the 5’ to 3’ direction.
What is the difference between the leading and lagging strands?
The leading strand is synthesized continuously towards the replication fork, while the lagging strand grows away from the fork in segments called Okazaki fragments.
What is the function of DNA Polymerase I?
DNA Polymerase I proofreads and edits newly synthesized DNA, correcting errors by cutting out incorrect bases and inserting the correct ones.
What is the end result of DNA replication?
The end result is two identical double-stranded DNA molecules, each containing one original and one newly synthesized strand, making the process semi-conservative.
Why is DNA replication important?
DNA replication is crucial for heredity, gene expression, and maintaining continuity of a species through genetic stability and variation.
What is the location of prokaryotic DNA?
Cytoplasm (chromosomal DNA located in nucleoid region)
What is the location of eukaryotic DNA?
Nucleus
What is the chromosomal structure of prokaryotes?
One circular loop (small plasmid is separate)
What is the chromosomal structure of eukaryotes?
Multiple linear chromosomes
How is prokaryotic DNA packaged?
Not associated with histones. Supercoiled around dense proteins
How is eukaryotic DNA packaged?
Associated with histones (supercoiled)
Do prokaryotes have introns?
No, prokaryotes do not have introns
Do eukaryotes have introns?
Yes, eukaryotes have introns that can be spliced out
What is the size of prokaryotic genomes?
Small genome, not complex
What is the size of eukaryotic genomes?
Larger genome, complex
What is the process of polypeptide synthesis?
DNA → (transcription) → mRNA → (translation) → polypeptide
Define gene expression.
When a cell is actively using a certain gene to make polypeptides
What is a polypeptide?
A series of amino acids joined together to form a unit
How is a protein formed?
One or more polypeptides twisted together into a particular shape
What determines the configuration of a protein?
The sequence and arrangement of amino acids
What are the key components of polypeptide production?
DNA, mRNA, tRNA, ribosomes, enzymes
What occurs during transcription?
The code on a DNA strand is written onto a strand of mRNA
What binds to the promoter during transcription?
RNA polymerase
How do ribonucleotides pair during transcription?
Uracil (U) on a ribonucleotide pairs with Adenine (A) in the DNA strand
In what direction does RNA polymerase build an RNA strand?
5’ to 3’ direction
What signals the completion of mRNA?
Sequences on the DNA called terminators
What is the non-coding strand?
The strand that contains genetic information to make the protein
What is the coding strand?
The other strand with the same sequence as the mRNA being made
Where does mRNA move after transcription?
Out of the nucleus and into the cytoplasm
What is the role of tRNA in translation?
Carries amino acids to the ribosome to make proteins
How do tRNA molecules attach to mRNA?
By pairing tRNA anticodons with complementary codons on the mRNA
What does the tRNA with methionine bind to?
The ‘start’ codon on the mRNA
What happens to tRNA after the amino acids are linked?
The first tRNA is released from the ribosome
What happens when a ‘stop’ codon is reached?
The polypeptide chain is released into the cytoplasm
What is pre-mRNA?
RNA straight from DNA with all introns and exons
What happens during RNA processing?
mRNA is edited, all introns removed, and exons spliced together
What is added to the 5’ end of the RNA?
A 5’ cap
What is added to the 3’ end of the RNA?
A poly-A tail (tail of A nucleotides)
What is mature mRNA?
Fully edited mRNA that can travel out of the nucleus
What does polypeptide synthesis provide?
Components necessary for protein formation (proteins and enzymes)
What is primary protein structure?
The sequence of amino acids linked to form a polypeptide chain
What is secondary protein structure?
Local folded structures that form due to interactions between backbone atoms
Define alpha helix.
A coiled arrangement of proteins consisting of a single chain stabilized by hydrogen bonds
Define beta-pleated sheet.
Anti-parallel chains of amino acids linked by hydrogen bonds forming a twisted, pleated sheet
What is tertiary protein structure?
The overall three-dimensional arrangement of a protein’s polypeptide chain
What is quaternary protein structure?
Proteins made up of multiple polypeptide chains (subunits)
Define allele.
A specific version of a gene
Define genotype.
The genetic makeup of an individual organism
Define phenotype.
Observable characteristics or traits of an organism
How do environment and genotype influence phenotype?
Phenotype depends on both genes and environmental factors
What effect does soil pH have on hydrangeas?
Acidic soil results in blue flowers, alkaline soil results in pink flowers
Define epigenetics.
Study of changes in organisms caused by modifications of gene expression
How do chemical modifications affect gene expression?
They may affect the density of DNA binding and gene switching on or off
Define genetic variation.
Genetic variation refers to the diversity in gene frequencies within a population, which leads to different traits among individuals.
What are homologous chromosomes?
Chromosomes that occur in pairs, with corresponding pairs known as alleles (different forms of genes) along each member of the homologous pairs.
Define dominant alleles.
The form of a gene that is expressed in heterozygous conditions, masking the recessive form of the same gene.
Define recessive alleles.
The form of a gene that is only expressed in homozygous conditions and is masked in heterozygous conditions by the dominant form of the same gene.
What is a hybrid?
An individual carrying different alleles (heterozygous) for a specific trait.
What is a purebred?
An individual carrying the same alleles (homozygous) for a specific trait.
Define monohybrid.
An individual that has contrasting factors for one characteristic; monohybrid inheritance is the inheritance of a single pair of contrasting characteristics.
What is Mendel’s Law of Dominance?
When parents with pure, contrasting traits are crossed together, only one form of the trait appears in the next generation, leading to a 3:1 ratio of dominant to recessive traits.
Define Mendel’s Law of Segregation.
During gamete formation, each gene separates so that each gamete carries only one allele for each gene.
Explain Mendel’s Law of Independent Assortment.
The alleles of two or more different genes get sorted into gametes independently of one another during gamete formation.
Define sex-linked traits.
Traits carried on sex chromosomes, where gene mutations can be present on X or Y chromosomes.
Give an example of an X-linked trait.
Hemophilia, a disorder affecting blood clotting, is an example of an X-linked trait.
Explain incomplete dominance.
A genetic scenario where the phenotype of the offspring is a blend of the traits of the two parents, resulting in an intermediate phenotype.
Define codominance.
A genetic scenario where both alleles are expressed, resulting in a new phenotype.
What does population genetics study?
The study of how a gene pool changes over time, understanding variation, and predicting the potential for populations to adapt.
Define allele frequency.
The ratio of the number of copies of a specific allele in a population to the total number of copies of all alleles for that gene in the population.
What is the Hardy-Weinberg Principle?
A principle stating that in a large, randomly mating population, allele frequencies will remain constant from generation to generation in the absence of other evolutionary influences.
Define polymorphism.
The presence of two or more alleles for a gene that exist in at least 1% of the species population.
What are single nucleotide polymorphisms (SNPs)?
Genomic variants at a single base position in the DNA, where a single nucleotide differs from the norm in at least 1% of the population.
What is DNA profiling?
The testing of specific profiles of an individual’s DNA, including short tandem repeats (STRs), to identify and compare individuals by characteristics in their DNA.
Explain the process of PCR (Polymerase Chain Reaction).
A method used to amplify desired regions of DNA by repeating cycles of denaturation, annealing, and extension, using a heat-resistant DNA polymerase.
What is gel electrophoresis?
A technique used to separate molecules such as proteins and nucleic acids based on size and charge by applying an electric current through a gel.
What are STRs (Short Tandem Repeats)?
Short sections of DNA with repeating nucleotides, which are valuable for identification purposes due to their variation in the number of repeating units among individuals.
Define epigenetics.
The study of changes in organisms caused by modifications of gene expression rather than alterations of the genetic code itself.
What is the Multiregional Hypothesis?
A theory proposing that modern humans evolved from multiple regional populations across the world.
Explain gene flow vs. replacement in human evolution.
Multiregionalism emphasizes gene flow and continuity between populations, while the Out of Africa model focuses on the replacement of existing populations by modern humans migrating out of Africa.
What does the Sanger Method entail?
A DNA sequencing method that involves isolating a DNA sample, amplifying it using PCR, adding fluorescent chain-terminating nucleotides, sorting fragments by length, and analyzing the sequence.
Describe the Maxam-Gilbert Method.
A DNA sequencing method that involves radioactively labeling DNA, using chemicals to cleave bases, and determining the sequence by gel electrophoresis of the resulting fragments.
What are the limitations of DNA profiling?
Evidence could be contaminated, and small amounts of contamination are magnified in PCR analysis of STRs, potentially leading to inaccurate results.
Explain the relationship between genotype and phenotype.
Genotype refers to the genetic makeup of an individual, while phenotype refers to the observable characteristics, influenced by both genetics and environmental factors.
Define reproduction.
Reproduction is the production of offspring in order to continue a genetic lineage and ensure the continuity of a species.
What are the two types of reproduction?
Sexual reproduction requires two parents, while asexual reproduction only requires one parent.
What are the characteristics of sexual reproduction?
Occurs in most multicellular organisms, offspring have genetic variation (meiosis), takes a relatively long time, and passes genetic information to the next generation (e.g., pollination, fertilisation).
What are the characteristics of asexual reproduction?
Occurs in unicellular organisms, offspring are genetically identical to the parent (except for mutations), takes a relatively short time, and also passes genetic information to the next generation (e.g., budding, cloning, fragmentation, binary fission).
Define fertilisation in the context of reproduction.
Fertilisation is the fusion of two gametes, which can occur both inside and outside the body, resulting in a zygote with the full diploid complement of chromosomes.
What are the requirements for fertilisation?
Both male and female gametes need to be produced and ready at the same time, arrangements are required to bring the gametes in contact, and water needs to be present to prevent drying out and allow sperm to swim to the female gamete.
What is internal fertilisation?
The union of an egg and sperm cell during sexual reproduction inside the female body, typically occurring in land animals.
What is external fertilisation?
The union of male and female gametes after their release outside the female body, typically occurring in aquatic organisms.
Define pollination.
The transfer of pollen from the anther to the stigma, leading to fertilisation inside the ovule contained in the ovary.
What is self-pollination?
The process where pollen from a flower’s anther pollinates the stigma of the same flower, resulting in no genetic variation.
What is cross-pollination?
The process where pollen from a flower’s anther pollinates the stigma of a different flower, ensuring greater variation in offspring.
How does pollination by wind work?
Pollen is transported by wind (anemophily), which is inefficient, requiring the production of larger quantities of pollen.
How does pollination by animals work?
Pollen is transported by animals (zoophily), requiring structures to attract pollinators such as scent, colour, markings, shape, and nectar.
Define seed dispersal.
The spreading of seeds away from the parent plant to cover widespread areas and ensure species continuity, minimizing competition for space, light, and nutrients.
What is germination?
The process by which a plant grows from a seed into a seedling, starting when a suitable soil environment is found, allowing the embryo to begin growing via mitosis.
Define vegetative propagation.
A process in which plants reproduce from stems, roots, and leaves, forming new plantlets without genetic variation.
What is budding?
A type of asexual reproduction where a new organism is formed from a bud of an existing organism, allowing rapid propagation without genetic changes.
What is the ovarian cycle?
Refers to the growth and maturation of an oocyte in preparation for fertilization and reproduction, repeating approximately every 28 days unless the female is pregnant.
Describe the follicular phase of the ovarian cycle.
The initial phase where the egg develops in the follicle, stimulated by FSH and LH from the pituitary gland, leading to the release of oestrogen and progesterone as follicles mature.
What happens during ovulation?
A dominant follicle releases chemicals encouraging the nearby fallopian tube to surround it, triggered by a surge in LH from the pituitary gland, resulting in the release of the egg into the fallopian tube.
What occurs during the luteal phase?
The ruptured follicle forms a corpus luteum, producing oestrogen and progesterone to prepare the uterus for pregnancy. If no fertilization occurs, the corpus luteum degenerates, decreasing hormone levels.
What is menstruation?
The breakdown of the endometrium accompanied by bleeding, marking the shedding of the uterine lining from the previous cycle.
Describe the secretory phase of the menstrual cycle.
The corpus luteum produces progesterone and oestrogen, thickening the uterine lining in preparation for possible implantation of a fertilized ovum.
What are the effects of FSH?
Follicle Stimulating Hormone (FSH) helps control the menstrual cycle by stimulating follicle growth and egg maturation in the ovaries.
What is the role of LH?
Luteinising Hormone (LH) promotes final maturation of the ovarian follicle, ovulation, development of the corpus luteum, and stimulates testosterone secretion.
What role does oestrogen play?
Oestrogen promotes growth of the uterine lining prior to ovulation, stimulates follicle growth, increases uterine responsiveness to oxytocin, and stimulates FSH and LH before ovulation.
What is progesterone’s function?
Progesterone, secreted by the corpus luteum and later by the placenta, prepares for implantation, stimulates growth of blood vessels supplying the endometrium, and inhibits uterine contractions to protect the fetus after implantation.
What is the role of oxytocin?
Oxytocin stimulates uterine contractions during childbirth and increases the contractions of breast tissue to aid in lactation after childbirth.
What is hCG (Human Chorionic Gonadotropin)?
hCG stimulates the corpus luteum to produce progesterone, maintaining pregnancy.
Describe the fertilisation process.
Sperm cells travel into the oviduct, where they push past residual follicle cells, bind to receptors on the zona pellucida, release enzymes to dissolve it, and fuse with the egg membrane, allowing the sperm nucleus to enter the ovum, forming a diploid zygote.
What occurs during implantation?
Seven days post-fertilisation, the zygote divides and migrates into the uterus, embedding itself into the nutrient-rich endometrium, now termed a blastocyst, which provides oxygen and nutrients to the growing embryo.
Evaluate the impact of scientific knowledge on the manipulation of plant and animal reproduction.
Scientific knowledge has enabled advancements in agriculture through techniques like selective breeding, genetic engineering, and cloning, enhancing crop yield, disease resistance, and overall efficiency in food production, while also addressing ethical considerations.
