DHS Honors Biology (O'Malley) Unit 6: Patterns of Inheritance

Meiosis

* 1 Diploid Cell to 4 Haploid Cells
* Two Stage Cell Division
* Sexual Reproduction results in the reproduction of gametes (sperm or egg cells)

Mitosis

* 1 Diploid cell to 2 Diploid cells
* Division of nucleus during cell division in an organism
* Occurs in both sexual and a-sexual organisms
* A-Sexual Reproduction

A-Sexual Reproduction

A single individual passes a copy of all its genes to the next generation.

Sexual Reproduction

Two parents pass unique combinations of both their genes to the next generation

Synapsis and Crossing Over

* Occurs during prophase I
* Homologous chromosomes pair together forming a tetrad
* Non-sister chromatids exchange information

Oogenesis

* Development of egg cells via meiosis
* Produces 1 viable ovum
* Produces 3 un-viable polar bodies
* Females are born with a set number of future egg cells

Ovum

Another term for an egg cell

Un-Viable Polar Bodies

Egg cells that cannot function due to lack of nutrients

Spermatogenesis

* The continous production of sperm
* Produces 4 sperm cells

Mendel

* The father of genetics
* Austrian Monk
* Law of Segregation
* Law of Independent Assortment

Mendel Pea Plant Experiment

* Uses technique of cross pollination to establish true breeding line of pea plants
* Removed male and female parts of the plant and breeded a new plant
* Through breeding, Mendel created eight completely dominant traits in pea plants

Law of Dominance (Mendel)

The dominant allele will always be fully expressed

Law of Segregation (Mendel)

Allele pairs separate during gamete reformation and randomly reform during fertilization

Law of Independent Assortment

Each Allele pair segregates Independent during gamete formation when genes for two different characteristics are located on different pairs of homologous chromosomes

Types of Linked Genes

Linked → (Close together increases chances)

Not Linked →(At different parts of the chromosome)

Non-Disjunction

When homologous chromosome pairs (sister chromatids) do not divide correctly resulting in too many or too few chromosomes.

Monosomy

Missing one chromosome from pair (1 in a pair)

Trisomy

One too many chromosomes (3 in a pair)

Aneuploid

Extra presence or absence of a chromosome pair ±1 chromatids

Sex Chromosomes

Chromosomes involved in sex (XX or XY)

Autosomes

Non-sex chromosomes

Down Syndrome

Trisomy in chromosome 21

Turner Syndrome

Monosomy in X chromosome

Klinefelter Syndrome

XXY (Male has an extra X)

Types of Fetal Testing

* Amniocentesis
* Chorionic Villus Sampling

Homologous Pairs

Chromosome pairs that have the same gene containing variations of the same trait.

Genomic Imprinting

Certain genes are turned off or on depending on who the gene was inherited from. Sometimes the mother or father gene is silenced and the other one is the only gene left.

Sister-Chromatids

The two sides of the "X" on for the chromosome

Gene

A unit of DNA which carries the genetic information necessary to synthesize specific proteins which represent heritable features

Trait

Each variant for a heritable feature

Phenotype

The traits that an organism expresses

Allele

Alternate variations of a gene

Dominant Allele

In a heterozygous condition, the allele that is fully expressed

Recessive Allele

In a heterozygous condition, the allele that is masked

Epigenetics

* Non-coding DNA
* Acetylation
* Methylation
* RNA Interference
* RNA Transcription Factors

Genotype

The genetic makeup of an organism

Homozygous Dominant

Having two identical dominant alleles for a trait

Homozygous Recessive

Having two identical recessive alleles for a trait

Heterozygous

Having a dominant and recessive allele for a trait

Monohybrid Cross

* Complete Dominance
* A cross between parents which are homozygous for different alleles for the same trait.
* The F1 generation is all heterozygous

P1 Generation

True breeding parents

F1 Generation

First hybrid offspring from parent generation

F2 Generation

Result of the F1 hybrids crossing

Incomplete Dominance

Inheritance where F1 hybrids have an appearance which is a mix between the phenotypes. (Like mixing/blending paint)

Dihybrid Cross

* A cross between parents homozygous for two different alleles.
* Results in an F1 generation that is a hybrid for both traits
* 9:3:3:1 Ratio

Dihybrid Cross Ratio (AaBb \* AaBb)

Key

D - Dominant

d - Recessive

\
Ratio

* 9 (DD)
* 3 (Dd)
* 3 (dD)
* 1 (dd)

Sex-Linked Traits

* Used to observe the inheritance patterns for sex chromosomes
* Since males are XY they are more likely to get recessive sex linked traits than females

Dosage Compensation

* X inactivation
* In females, one X chromosome is inactive in every cell
* Females are a mosaic of their parents because the paternally inherited X chromosome is activated in some cells and the maternally inherited X chromosomes is activated in the others

Multiple Alleles

* Genetic trait that has more than 3 phenotypes
* Example: Blood Types

ABO Blood Typing

* Matching blood types is important for transfusions
* Antibodies on the antigens on incompatible blood types don't like to mix and this causes clotting

Rh Factor

* Indicates positive or negative blood type
* Rh^- mother with Rh^+ father could causes complications

Antibodies

“Police Patrol” identifying things that should not be there

Antigen

A toxin or other foreign substance

Multifactorial Traits (Polygenic)

* Traits affected by multiple genes
* Most traits are _____

Quantative Characters

How you classify the trait by measuring it in some way

Epistasis

One gene altering the expression of another gene

Autosomal Dominant Trait

* A single abnormal gene on one of the first 22 nonsex

Autosomal Recessive Trait

Non-sex recessive

Sex-Linked Traits

Traits taht are passed in the sex chromsomes

Pedigree

A chart that diagrams the inheritance of a trait or health condition through generations of a family.

Mutations in Gametes

Cannot lead to changes in future generations