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Genetics

Genetics Study of how traits are inherited through the interaction of genes

Heredity The passing on of traits from parent to offspring EX: blue eyes, brown hair, or a hitchers thumb

Trait Characteristics that are inherited EX: A characteristic, is tallness or shortness, blue eyes or brown eyes

Alleles Different forms of a trait that a gene may have Each sex cell (sperm or egg) has 1 allele for each trait EX: 1 allele for Tallness EX: 1 allele for Shortness

Dominant Trait Dominant- a trait that is expressed and covers up the recessive form It is always written as an Uppercase letter EX: for the allele of Tallness, you will use the letter T You only need 1 dominant allele for a trait to show

Since tallness is dominant, she will be tall either way EX: Tallness TT or Tt Since tallness is dominant, she will be tall either way Only Need 1 Dominant Trait

Recessive Trait Trait that can be masked by the dominant trait ALWAYS use a lowercase letter and it goes second EX: For shortness you would use a lowercase t Tt or tt

Recessive You NEED 2 alleles for a recessive trait to show EX: tt

trait masks the recessive The dominant trait masks the recessive LOWERCASE because it’s RECESSIVE Tt tt

Genotype The genetic makeup The allele combination of an organism EX: Tt, TT, or tt

Phenotype The way an organism looks and behaves EX: tall, short, blue eyes, brown eyes You can’t always tell what a genotype is by looking at someone’s phenotype

Phenotype

Heterozygous or Hybrid Offspring has different forms of trait EX) Dd, Tt, or Bb

Homozygous Same forms of a trait EX: DD, TT,tt, bb, BB

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Gregor Mendel He was the “father of genetics” He studied Pea Plants He was the first person to successfully predict outcomes of specific traits He came up with the 3 Laws of heredity

Mendel’s Laws of Heredity 1) Rule of Unit Factors 2) The Law of Segregation 3) The Law of Independent Assortment

The Rule of Unit Factors: An organism has 2 alleles for a trait The 2 alleles are on different copies of chromosomes, one from the female parent & one from the male parent EX: Tt, TT, or tt

B and b come from MALE B and b come from Female

The Law of Segregation Each gamete (sex cell) receives 1 allele for a trait from each parent During fertilization, the gametes randomly pair

The Law of Segregation What is happening to the A and a from the dad? What is happening to the A and a from the mom

The Law of Independent Assortment Genes of different traits are inherited INDEPENDENTLY and RANDOMLY of each other EX: The height of a plant and color of the seed are inherited independently of each other

color and shape of the seed Pea Plants Their traits are color and shape of the seed

Mistakes in Meiosis

Non-Disjunction a type of mistake in meiosis that happens to the CHROMOSOME It is the failure of homologous chromosomes to separate properly

2 things can happen a) Have extra chromosomes b) Missing chromosomes

Extra Chromosomes EX: Down Syndrome When chromosome # 21 does not fully separate, and there is an additional chromosome A person with down syndrome has 3 chromosomes instead of 2, which is called Trisomy 21 Instead of having 46 chromosomes, they have 47

Extra Chromosome EX: Polyploidy Polyploidy is when there is a total LACK of separation of homologous chromosomes The gamete (sperm/egg) inherits an entire EXTRA set of chromosomes

Polyploidy Polyploidy is rare in animals, but if it occurs it will result in death of a zygote BUT, it is frequent in PLANTS Plants that have polyploidy are larger, healthier, and are of greater commercial value

Polyploidy

Missing Chromosomes If a chromosome is missing, the organism will most likely not survive It is referred to as “monosomy” EX: Turner syndrome

Human females have only 1 single X chromosome instead of 2 X’s Turner Syndrome

How to detect Genetic Disorders Cells are extracted from a person The Cells are stained to reveal a banding patterns Chromosomes are identified, and arranged in homologous pairs This chart is called a Karyotype, and is used to detect chromosomal abnormalities

Chromosomes # 1-22 are called Autosomes

Sex Determination: Chromosomes # 23

ADD THIS PLEASE SPERM determines the sex of a child The sperm is either X or Y The egg is ALWAYS a X XX is female XY is male