Genetics: Study Notes Biology Genetics Test 2

SBI3U Grade 11 Biology Genetics Test 2 Genetics Study Notes Genetics: the branch of biology that studies how genetic information is carried fromone generation to the next, as well as heredity and variation in living things Genetics: study of heredity, the process by which a parent transfers specific genes totheir children; children inherit the genes that exhibit particular features from their biological parents. DNA: molecule inside the nucleus that gives instructions to make proteins etc. DNA Nucleotide includes: ● 1 Phosphate group ● 1 Deoxyribose Sugar ● 1 Nitrogenous Base (Adenine, Thymine, Guanine, Cytosine) Base Pair: AT and CG ● Gene: segment of DNA that encodes information Meiosis: process at which sex cells (gametes) with a haploid number of chromosomes are produced Two Key Outcomes: 1. Genetic Reduction: daughter cells produced have half the amount of genetic information (23 chromosomes) 2. Genetic Recombination: products have different combinations of alleles (forms of a gene), genetically different offspring Meiosis: ● takes place in ovaries and testes ● two nuclear divisions ● human cell with 46 chromosomes (2n) will undergo meiosis, producegametes with 23 chromosomes (n), known as gametogenesis ● each gamete has 23 chromosomes ● produces 4 haploid daughter cells that are genetically different

● fertilization: haploid (n) sperm cell + haploid (n) egg cell = diploid (2n)zygote ● zygote will produce multicellular organism Vocabulary: Chromosomes- humans have 46, 23 pairs, 1 pair of sex chromosomes, 22 pairs ofautosomes, 2 sister chromatids held by a centromere- chromatins Centromere- middle region of chromosome, attracts spindle fibers Somatic cells- body cells (non-sex cells), undergo mitosis Haploid (n)- half the genetic information (23 chromosomes) Diploid (2n)- complete set of genetic information (46 chromosomes) Homologous chromosomes (tetrad)- pair of chromosomes similar in shape, size,gene arrangement and gene information (not identical as they may carry different forms of the same gene) (Example: Chromosome #1) Synapsis- pairing of homologous chromosomes, during prophase 1 in meiosis 1 Crossing over- exchange of chromosomal segments between a pair of homologouschromosomes Cytokinesis- division of cytoplasm (two cells produced) Meiosis 1: first division, chromosome number reduced in half, synapsis and crossing over occur Interphase 1: ● DNA double (46-92) Prophase 1: ● each pair lines up side by side (synapsis) ● segments of chromosomes exchanged (crossing over) ● centrioles move to poles ● spindle apparatus forms

Metaphase 1: ● pairs of homologous chromosomes line up along the equator (middle of cell) ● spindle fibers attach to centromere of each homologous chromosome (where centromeres end up is random) Anaphase 1: ● homologous chromosomes separate ● move to opposite poles (segregation) ● one chromosome (two chromatids) move to pole, now haploid ● errors likely to occur here as chromosomes divide into new cells Telophase 1: ● chromosomes begin to uncoil ● spindle fibers disappear ● cytokinesis takes place ● nuclear membrane forms around each group of chromosomes ● diploid cells (46 chromosomes) Meiosis 2: second division, no replication of genetic material, 4 haploid cells produced at the end, all are genetically different Prophase 2: ● nuclear membrane disappears ● centriole pairs move to opposite ends ● spindle fibers reform ● chromosomes condense Metaphase 2: ● sister chromatids attach to spindle fibers in middle of the cell Anaphase 2: ● sister chromatids are pulled apart to opposite sides of the cell ● errors likely to occur here as chromosomes divide into new cells

Telophase 2: ● nuclear membrane reforms around sister chromatids ● centriole pairs disappear ● DNA uncoils ● cytokinesis occurs Gamates: ● production of egg and sperm cells (4 egg, 1 sperm) ● haploid= 23 chromosomes ● daughter cells are not identical to parent cell Importance of Meiosis: ● Genetic variety within individuals is a result of crossing over andindependent assortment. ● independent assortment: where chromosomes end up when they splitand go to the poles, different genes go both ways (occurs in Anaphase 1 and 2) ● crossing over: genetic material is mixed with that of the other in the homologous pair, creates a mix of genes when new cells are formed(occurs in prophase 1) ● most gamete cells receive mix of paternal and maternal chromosomes Gametogenesis: ● production that creating a sperm or egg ● differs greatly between spermatogenesis and oogenesis ● spermatogenesis: converts the spermatocyte into four spermatids ● Oogenesis: asymmetric cell division creates three tiny cells, three polar bodies, and one giant cell. ● during birth, eggs are produced until prophase 1, meiosis will continue for one cell each month beginning at puberty, final stage of meiosis 2 isnot completed unless fertilized ● when meiosis 2 is completed, the mature egg (n) has been fused with asperm cell (n) to create a diploid (2n) zygote Abnormal Meiosis: Nondisjunction: ● occurs when two homologous chromosomes move to the same pole during meiosis 1 ● results in one of the daughter cells having an extra chromosome, while the other is missing one

● cells do not function properly ● can also occur in any cell if chromatids do not separate ● three of one chromosome: trisomy ● one less chromosome: monosomy Chromosomal disorders: Down syndrome: Extra chromosome 21 ● intellectually disabled ● heart defects ● physical abnormalities Klinefelter syndrome: Extra X chromosome ● occurs in males (extra female chromosome) ● tall and slim ● few pubic hair, facial hair and underarm hair Turner Syndrome: missing X chromosome ● occurs in females ● short stature ● sterile ● lack of ovarian development ● poor breast development ● no menstruation *Disorders affecting autosomes have the greatest effect on a person’s health as theyimpact genetic info and behavior. *XX= Female, XY= Male Vocabulary: Chapter 5: Alleles: two or more variations of a gene, alleles are located at the same position on a pair of homologous chromosomes Dominant: alleles of this type determine the expression of the genetic trait (capital letter)

Recessive: alleles of this type are “masked” by dominant alleles (lower case letters) Phenotype: the observable trait of an organism (eg. hair and eye color) Genotype: the alleles that make-up a gene (specific trait) (eg. AA, Aa, aa) Homozygous: a genotype in which the allele pairs are the same (eg. AA or aa) Heterozygous: a genotype that includes a dominant and a recessive allele (eg. Aa) Mendelian Genetics: Mendel’s Law of Heredity 1. Each parent contributes one allele during cross-fertilization. 2. Dominant allele is always expressed when the recessive allele is present. 3. Each pair of alleles segregates during formation of sex cells. Hybrid: the offsprings from two pure lines, often heterozygous Monohybrid Cross: cross where one trait is observed Dihybrid Cross: a cross where 2 traits are observed Monohybrid Crosses: (2×2 Punnett Square) -Does it with one trait at a time. -Demonstrates how dominance and recessive genes could be passed onto from one generation to another. P1 Generation: BB bb F1 Generation: Bb Bb Bb Bb F2 Generation: BB Bb Bb bb **F2 Generations will always have 3:1 ratio of dominance and recessive

Dihybrid Crosses: (4×4 Punnett Square) -Demonstrates Mendel’s law of independent assortment that the inheritance of one trait doesn’t dictated the inheritance of another -In Dihybrid crossing, 2 traits are put to the test Solving: Distributive property both genotypes *9:3:3:1 Ratio for two heterozygous Test Cross: ● use when the genotype of 1 parent is unknown but they express a dominant phenotype ● parent is crossed with a homozygous recessive parent ● determining whether or not the parent is homozygous dominant orheterozygous ● two cases for monohybrid ● four cases for dihybrid Incomplete Dominance: ● not all alleles are fully dominant or recessive ● heterozygous genotype can show an intermediate phenotype (blending ofalleles to produce a new phenotype) ● occurs when two alleles are equally dominant, produce a newheterozygous genotype ● example: red dragon + white dragon = pink dragon Codominance: ● occurs when both alleles are fully expressed ● one allele does not mask the other ● example: red bull + white cow = roan calf (mix of white and red hair thatappears in patches) Lethal Alleles: ● alleles that have a detrimental effect on the organism ● if lethal gene is dominant and expressed immediately, organism woulddie, eliminate gene from population ● if organism lives long enough to reproduce, gene is passed on to nextgeneration

ABO Blood Group: ● system shows both multiple alleles and codominance, more than two alleles possible for a given name Genotype Phenotype IAIA or IAi -dominant Type A IBIB or IBi –dominant Type B IAIB – dominant Type AB ii –recessive Type O Sex-linked Inheritance: ● traits controlled by genes on either the X or Y chromosome are calledsec-linked traits ● they are identified by their different rate of appearance between thegenders ● most X-linked traits are recessive, affected male passes the allele ontodaughter ● females must inherit both alleles to be affected while males only needone ● only females can be carriers ● example: CVD- color vision deficiency, hemophilia