Unit 6 - Inheritance of Traits Study Guide

Definition: The purpose of meiosis is to produce gametes, which are haploid cells, needed for reproduction.

Crossing Over: The exchange of genetic information between homologous chromosomes.
Diploid Cell: A cell that contains two complete sets of chromosomes (2n).
Gametes: Cells produced through meiosis used during sexual reproduction.
Haploid Cell: A cell that contains one complete set of chromosomes (n).
Homologous Chromosomes: Pairs of inherited chromosomes, one from each parent.
Somatic Cell: A body cell in which the number of chromosomes does not change.

Anaphase I: Homologous chromosomes separate.
Anaphase II: Sister chromatids separate.
Meiosis I: Chromosome number is reduced by half (from 2n to n).
Meiosis II: Cell division that is most similar to mitosis.
Metaphase I: Homologous chromosomes line up along the center of the cell.
Metaphase II: Chromosomes (pairs of sister chromatids) line up along the center of the cell.
Mitosis: Nuclear membrane reforms, cytokinesis to form two daughter cells begins.
Telophase I: Nuclear membrane reforms, cytokinesis to form two daughter cells begins.
Prophase I: Crossing over occurs.
Telophase II: Nuclear membrane reforms, cytokinesis to form four daughter cells begins.
Prophase II: Not specifically mentioned, but might refer to the preparation for the second division of meiosis.

Note: Be sure to match sketches of the different phases with their description. This emphasizes the understanding of processes like crossing over which occurs only during Prophase I.

Who was Gregor Mendel?: He studied the inheritance of traits and is considered the father of genetics.

Allele: Different versions of the same trait.
Dominant: This version of the allele will always show if present.
Fertilization: The combining of female and male gametes.
Hybrid: Offspring of crosses between parents with different traits.
Recessive: The version of the allele that only shows if there are two copies.
Genotype: The allele combination an individual inherits.
Phenotype: The observable trait of an individual.

Principle of Dominance: Some alleles are dominant and some are recessive; the dominant trait hides the recessive trait (e.g., short vs. tall pea plants).
Principle of Segregation: The two alleles for a trait are separated when gametes are produced (during anaphase I).
Principle of Independent Assortment: Alleles for different traits segregate independently of each other (during metaphase I).

Labeling: Understand how to label heterozygous, homozygous dominant, homozygous recessive, genotype of offspring, and parents inside and outside the square. Example:
- Punnett Square template:
- Parents: AA (homozygous dominant) and aa (homozygous recessive) - Offspring genotypes: AA, Aa, aa
Phenotypic Ratio: Ratio of observable traits in offspring derived from Punnett square calculations. Example from long (A) vs. short (a) hair: 3 long to 1 short.

Pea Plants Example:
- Yellow (Y) vs. Green (y): Cross homozygous green peas (yy) with heterozygous yellow peas (Yy). Possible genotypes and phenotypes derived from Punnett Square.
- Genotype Ratio: 1YY : 1Yy : 0yy - Phenotype Ratio: 2 yellow : 2 green
Homozygous vs. Heterozygous: Cross a homozygous tall (TT) with a heterozygous tall (Tt). - Possible genotypes: 2TT : 2Tt - Phenotype: All tall.

Karyotypes: Used to determine chromosome abnormalities and biological sex.
- Example with karyotype: Female identified with XX. - Genetic Disorders: Disorders identified through karyotypes such as trisomy-21 (Down syndrome).
Difference between Autosomes and Sex Chromosomes: - Autosomes: Chromosomes that do not determine sex. - Sex Chromosomes: Determine biological sex, specifically the X and Y chromosomes (XY for males and XX for females).

The central dogma states that genetic information flows from DNA to RNA to protein: $ext{DNA} ightarrow ext{RNA} ightarrow ext{protein}$ .

Different Types of RNA:
mRNA (Messenger RNA): Carries genetic code from the nucleus to the ribosome, single-stranded.
tRNA (Transfer RNA): Matches anticodon to codons to bring amino acids in sequence.
rRNA (Ribosomal RNA): Makes subunits of the ribosome.

Transcription: Takes place in the nucleus, catalyzed by enzyme RNA polymerase.
Translation: Takes place at the ribosome, where mRNA is read to form proteins with assistance from tRNA.

Codon: A sequence of three nucleotides on mRNA that codes for an amino acid.
Start Codon: First codon for every protein is $AUG$ which reads as methionine.

Blood Types: Example of a cross between A (AA or AO) and AB. - Probabilities calculated for blood type offspring.
Sex-Linked Traits: Use of Punnett squares to predict phenotypes in sex-linked traits (e.g., eye color in fruit flies).
- Red eyes (R) dominant to white eyes (r).

Carriers: In sex-linked traits, females are carriers because they have two alleles while males only have one.

Genotypes: Assign genotypes for individuals on a pedigree, determining individuals that may express both normal and sickle-shaped red blood cells based on codominance.