Alleles And Inheritance Flashcards
What did the experiments on pea plants determine about traits?
Traits are determined by alleles for any given characteristic.
What does the combination of alleles in an organism represent?
Genotype.
What is the expressed trait of an organism called?
Phenotype.
What is the genotype of a yellow hybrid in pea plants?
Heterozygous (Yy).
Fill in the blank: The parental generation in genetics is referred to as the _______.
P generation.
What does homozygous mean?
Having two identical alleles for a given trait.
What is the significance of the genotype in determining phenotype?
The genotype determines the expressed trait (phenotype).
What does the Law of Segregation state?
During meiosis, the alleles of a gene separate randomly into individual gametes.
What is the definition of genotype?
The genetic constitution of an organism, represented by alleles.
What is the definition of phenotype?
The observable characteristics or traits of an organism.
What is a Punnett Square?
A grid used to show the probability of offspring’s genotype and phenotype.
What is the gamete genotype for a dominant yellow allele in pea plants?
Y
What is the gamete genotype for a recessive green allele in pea plants?
y
What is the phenotype ratio when two heterozygous pea plants are crossed?
75% yellow : 25% green (3:1)
What is the genotype ratio for offspring from a cross of two heterozygous pea plants?
1 YY : 2 Yy : 1 yy (1:2:1)
Fill in the blank: The dominant allele for color in pea plants is represented by _______.
Y
Fill in the blank: The recessive allele for color in pea plants is represented by _______.
y
What percentage of offspring will be homozygous dominant when crossing two heterozygous pea plants?
25%
What percentage of offspring will be homozygous recessive when crossing two heterozygous pea plants?
25%
What is a test cross?
To determine the presence of a recessive allele within an individual with dominant phenotype, by crossing them with a homozygous recessive individual
This helps identify if the dominant phenotype individual is homozygous or heterozygous.
What are the genotypes and phenotypes of the offspring from a cross between BB and bb?
Genotype: 100% Bb, Phenotype: 100% brown
This scenario demonstrates a cross between homozygous dominant and homozygous recessive.
What are the genotypes and phenotypes of the offspring from a cross between Bb and bb?
Genotype: 50% Bb, 50% bb; Phenotype: 50% brown, 50% blue
This scenario illustrates a cross between a heterozygous and a homozygous recessive individual.
If an individual produces only offspring with a dominant phenotype, what can be concluded about that individual’s genotype?
The individual is homozygous dominant
This means they carry two dominant alleles.
If an individual with a dominant trait produces even one offspring with a recessive phenotype, what can be concluded about that individual’s genotype?
The individual is heterozygous dominant
This means they carry one dominant allele and one recessive allele.
What is the Law of Independent Assortment?
The principle that alleles for different traits segregate independently of one another during gamete formation.
This law is a key concept in genetics and was first formulated by Gregor Mendel.
During which phase of meiosis does independent assortment occur?
Metaphase I.
In Metaphase I, homologous chromosomes align at the cell equator, allowing for independent assortment.
What is the genotype of a dihybrid cross?
AaBb.
A dihybrid cross examines the inheritance of two different traits.
What are the possible genotypes for a dihybrid cross between WwDd and WWdd?
- WWDd
- WwDd
- WWdd
- Wwdd
This is derived from combining the alleles of the two parents.
What are genes located on the same chromosome called?
Linked genes
Linked genes do not segregate apart during meiosis and are often recombined together.
What is the effect of linked genes on gamete genotypes?
Reduces the number of different possible gamete genotypes produced
This occurs because linked genes tend to be inherited together.
What are the sex chromosomes in humans?
X and Y chromosomes
These chromosomes determine an individual’s biological sex.
Where do most sex-linked traits occur?
On the X chromosome
This is typically represented as (X-linked) in Punnett squares.
What are two examples of X-linked traits?
Colourblindness, hemophilia, baldness
These traits are affected by alleles located on the X chromosome.
In X-linked traits, who is more affected by the recessive allele?
Males
Males have only one X chromosome, so they lack a second X chromosome that could mask the recessive allele.
Fill in the blank: Genes located on the same chromosome are typically ______.
linked
Linked genes do not segregate apart during meiosis.
True or False: All sex-linked traits are located on the Y chromosome.
False
Most sex-linked traits are located on the X chromosome.
