Inheritance of Traits Test - Honors Biology

On April 29, 2025

Heredity

the passing on of physical or mental characteristics genetically from one generation to another.

Gene

Sequence of DNA that determines specific traits

Codes for proteins (which ones kids can make, causing traits)

Passed from parent to offspring

Alleles

Different forms of the same gene

Alleles determine different versions of the same trait

Found in the same location on the chromosome

Dominant alleles

Overrules other allele if both are present

Recessive alleles

Overruled by other allele if both are present

Genotype

Which alleles are present

(Ex.: Rr [lettering])

Phenotype

Which traits are shown

(Ex.: Blue eyes)

Heterozygous

Ex.: Rr

Homozygous recessive

Ex.: rr

Homozygous dominant

Ex.: RR

Fertilization

Gametes (sperm,egg) fuse together to make a new individual

Simple dominance

There is a recessive allele and a dominant allele and when both alleles are present, the dominant trait is shown.

Incomplete dominance

“Blend”

R’ signifies incomplete dominance

Ex.: Red flower and white flower with Homozygous dominant and recessive genotypes fuse to make all pink flowers

Codominance

“Both traits at once”

Ex.: Same flowers (red and white), though different results (red, red/white, white)

Predicting 2 traits at once

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Autosomes (Autosomal Chromosomes)

Soma (body)

Humans have 22 pairs

Sex chromosomes

Each parent contributes 1

Humans have 1 pair, XX (f), XY (m)

Sex-linked traits

Traits that have alleles located on one of the sex chromosomes

Can be x-linked or y-linked

It is impossible for males to…

Be carriers of sex-linked traits (without showing it)

X and Y are not “dominant” over one another…

So traits show in the case of X*Y (color blindness ) (Colorblind male)

Pedigree

Family history of an individual signifying presence of traits, absences, and carriers

Presence of traits is represented by…

Filled in (black) circle/square

Absence of traits is represented by…

Not filled in (white) circle/square

Carrier of traits are represented by…

Half -filled square/circle

Square means…

Male

Circle means…

Female

Determining inheritance patterns on pedigrees..

• Are there carriers?

  • Yes - Autosomal recessive or x-linked

    • Are the carriers males or females

      • Males and females - Autosomal recessive

      • Females - X-linked

  • No - Autosomal dominant or y-linked

    • Are males or females affected

      • Males - Y-linked

      • Males and females - Autosomal dominant

Karyotype

The set of all chromosomes of an individual

Autosomal dominant/recessive traits

NOT Sex-linked (located on autosomes)