Bio Unit 8

Heredity

**passage of traits from parent to offspring**

Chromosomes

Condensed form of DNA

Diploid

Organisms like humans, contain chromosomes in pairs, one half of each chromosome pair comes from the male parent and the other half of the pair comes from the female parent, it has two matching (but not identical) homologues per set

Homologous Pairs

it is known as two matching (but not identical) __________ per set,

Humans Chromosomes

have 2 sets of 23 chromosomes, therefore 46 in total

Karyotype

picture of an individual’s chromosomes

Sex Chromosomes

23rd pair and they determine the sex of the offspring

Nondisjunction

causes chromosomes to not separate properly, can result in an abnormal chromosome number.  An abnormal chromosome number is damaging to the offspring

Monosomy

an individual has only one chromosome when it should have a pair, would have 45 total chromosomes

Trisomy

when an individual has an extra chromosome in a pair, have 47 total chromosomes

Downs Syndrome

Trisomy 21

Trait

any characteristic that can be passed from parent to offspring

Heredity

the passing of traits from parent to offspring

Genetics

the scientific study of heredity

Gregor Mendel

Pea plant experiment, father of genetics

Gene

 a DNA sequence that determines a particular trait for an organism

Locus

gene for a trait is always found in a specific location on a specific chromosome

Alleles

Genes can have different forms, dominant, recessive, represented by single letters

Roses

2/8 white roses, 6/8 red/pink roses

Dominant Allele

the stronger variant of a gene, it is usually expressed more often.  Represented by a capital letter (ex: R or T), If an individual has two ______ alleles (ex: RR or TT), they will show ______ trait, If an individual has one _____ allele & one ______ allele for a trait (ex: Rr or Tt), they will display the _______ trait

Recessive Allele

the gene that is displayed less often in a cross.  Represented by a lowercase letter (ex: r or t), If an individual has two ______ alleles (ex: rr or tt), they will show the ______ trait, If an individual has one ______ allele & one ______ allele (ex: Rr or Tt), they will not show the ________ trait

Genotype

allele combination for a trait, or the organism’s actual genetic makeup, codes for proteins, which code for traits, represented by two letters, one for each allele, homozygous or heterozygous

Homozygous genotype

gene combination of 2 dominant or recessive alleles  Ex: AA or aa

Heterozygous genotype

gene combination of one dominant and one recessive allele, called hybrid  Ex: Aa

Phenotype

is the physical trait resulting from a genotype, Ex: yellow or green coat color

Punnett Square

Offspring inherit alleles from their parents.  The probability that an offspring will inherit a specific combination of alleles (and therefore a particular trait) can be  predicted

Monohybrid cross

determine the probability that an offspring will inherit a single trait using a Punnett Square

Non-Mendelian traits

Some traits do not follow the patterns that Mendel observed

Incomplete Dominance

neither allele is completely dominant over the other and a blend of traits is observed

Codominance

in which both alleles are dominant and both are expressed equally, A capital letter represents one of the codominant alleles.  A different capital letter represents the other codominant allele so that the two are easily differentiated. Example: *Roan cattle exhibit codominance; they are brown and white spotted*

Multiple Alleles

(specifically **ABO Blood Types**), in which three alleles (two codominant and one recessive) determine human blood type,

Letter Prime (P’)

A capital letter represents one of the two incompletely dominant alleles.  The same capital letter, represents the other incompletely dominant allele

ABO Blood Types

Blood types are distinguished by the presence (or absence) of certain antigens, called A and B. on the surface of red blood cells, ABO blood type in humans is determined by *three* alleles: IA, IB, i, IA and IB are codominant alleles, Both IA and IB are dominant to the allele i, In this case, there are four different phenotypes (blood types): A, B, AB, and O

Type A can donate to

Type A and AB

Type B can donate to

Type B and AB

Type AB can donate to

Type AB

Type O can donate to

Type A, B, AB, and O

X-linked gene

one that is present on the X chromosome but not the Y chromosome.  This can lead to different patterns of inheritance, Due to the inheritance pattern of x-linked disorders in humans, certain conditions are much more common in men

Color Blindness and Hemophilia

two X-linked diseases that are more common in men than in women because of their pattern of inheritance, a mother who is heterozygous for one of these disorders: one of her X chromosomes has the allele and one does not

Hemophilia

blood clotting disorder in which the body has difficulty stopping bleeding.  Small cuts can be very dangerous for sufferers of hemophilia

Pedigree

to show the passing of traits in families, Circles represent females, squares represent males.  Whether or not a box is shaded is an indication of phenotype (recall that this is a physical trait).  *Shading indicates that a trait is shown*

Marriage Lines

Lines directly between individuals

Line of Descent

A vertical line from a marriage line

Sibling Lines

Branches off of the line of descent

When a pedigree is used, it is often to

Determine if a trait  is dominant or recessive, Determine if a trait is autosomal or sex-linked, Infer the genotype of an individual