Heredity by Brainpop I Heredity Genetics o The

Heredity by Brainpop

I. Heredity & Genetics o The passing of traits from parent to offspring o Traits are controlled by genes

II. ALLELES o ONE FORM of a gene o Sex cells have one o Body cells have two forms or ALLELES for a single gene o One may be dominant over another.

III. DOMINANT AND RECESSIVE o Dominant will always be expressed and will “mask” mask recessive o A recessive trait can only be expressed if there are no dominant alleles present.

o Example: Example Eyecolor—Brown color is dominant and blue is recessive.

• Dominant alleles are represented with a capital letter, recessive with a lower case letter.

IV. GREGOR MENDEL o “father of genetics”

o Mendel worked with peas

V. PROBABILITY o chance something will happen o Ex: heads or tails on a coin is 50% (1/2 chances) o more accurate with more trials

Why is it that if a couple has 2 children, they don’t always have one boy and one girl? 2 is a really small trial #…so won’t always “see” the ratio!

VI. Using a Punnett Square o Used to predict probability of traits o trait is given TWO letters, one for each allele.

GENOTYPE = Gene Combinations located on chromosomes o “Purebred” =BB or bb. o “heterozygous”(hybrid). Bb

o The PHYSICAL trait =PHENOTYPE o Blue Eyes.

Incomplete dominance • Heterozygous expresses a different phenotype

Multiple alleles - Blood type • 3 alleles, codominance A, B, o

4 blood types from 3 alleles • • AA or Ao= type A BB or Bo= type B AB = type AB oo = type O

Polygenic inheritance = many genes for one character.

SEX-LINKED and SEX INFLUENCED TRAITS

SEX CHROMOSOMES CAN CARRY OTHER GENES TOO = SEX LINKED TRAITS _________

Sex chromosomes can carry other genes Y-LINKED GENES: Genes carried on Y chromosome EX: Hairy pinna males. Y _______ linked genes only show up in __

Sex chromosomes can carry other genes X-LINKED GENES: Genes carried on the X chromosome EX: Hemophilia _______ Colorblindness _______ Duchenne Muscular Dystrophy _____________

SEX INFLUENCED TRAITS Genes not carried on ______ sex chromosomes BUT affected by ______ sex hormones of individual with gene

PEDIGREE CHART Normal Male = Normal Female = Has trait =

CARRIER Individual with one copy of a recessive autosomal allele NORMAL DEFECTIVE Carriers DON’T SHOW the trait themselves but can pass it on to their offspring

CHROMOSOMES

DNA Nucleic acid made of nucleotide subunits A T G C Found in nucleus Carries the genetic code in its sequence

DNA can appear in 2 forms Spread out in nucleus as CHROMATIN _______ in NON-DIVIDING cells Scrunched into bundles CHROMOSOMES in as ________ DIVIDING cells

Histone PROTEINS ____ • maintain shape of chromosome

Cancer cells • Don’t stop dividing Carcinogens damage DNA • ______ Ex: Radiation, cigarette smoke, chemicals in environment

CANCER

Chromosome structure CHROMATIDS • ______ 2 identical arms CENTROMERE • ______ constricted area holds chromatids together HOMOLOGOUS • _________ PAIR 2 of each chromosome (one from mom; one from dad)

CHROMOSOME NUMBERS • Each species has a characteristic number of chromosomes • HUMANS have 46 chromosomes (23 pairs)

DIPLOID & HAPLOID Cells with 2 copies of each chromosome are DIPLOID 2 n ________ (one from mom; one from dad) • All body cells Cells with only one copy of each chromosome HAPLOID 1 n are __________ • Sperm and egg 1 n egg + + 1 n sperm = 2 n new organism

KARYOTYPES KARYOTYPE ____ = picture of organism’s chromosomes

• Chromosomes that determine the sex of an organism = Sex chromosomes _____________ • All other chromosomes = _________ autosomes Humans have two sex chromosomes X y

A KARYOTYPE can tell the sex of an organism In humans XY is a male

In humans XX is a female

Guess who? XY

You can’t judge a critter by its chromosomes This critter has 54 chromosomes

Corn has 10 pair of chromosomes

Snails have 18 pairs of chromosomes

A mouse has 40 chromosomes

Nondisjunction • Chromosomes fail to separate during meiosis • gametes may have too few or too many chromosomes • Disorders: – Down Syndrome – three 21 st chromosomes – Turner Syndrome – single X chromosome – Klinefelter’s Syndrome – XXY chromosomes 45

Eric has Down’s Syndrome 1 in 750 births Has extra #21 chromosome Mental retardation

Down’s syndrome (trisomy 21) Simian line on palm Eye fold

Down’s syndrome (trisomy 21) • Most common chromosomal abnormality • 50% have heart defects • Mental retardation • Risk increases with age of mom

Patau syndrome (trisomy 13)

Patau syndrome (trisomy 13) • 1 in 7000 births (rare)

Patau syndrome (trisomy 13) Cleft lip & palate Eyes too small or missing

Patau syndrome (trisomy 13) Low set ears Polydactyly

TURNER’s SYNDROME • XOonly 1 X, no Y • Short stature • Immature ovaries • heart problems • hearing loss • decreased mental ability

Turner Syndrome Normal uterus, tubes and ovaries Non-functional Ovaries

Kleinfelter syndrome XXy

Kleinfelter syndrome • 1 in 1000 births • Male = XXy • Aslight decrease in intelligence • Small testes/can’t have children

Xyy syndrome • Xyy males • Taller, more aggressive