Mendel's Laws of Inheritance

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the key observation in the Law of Uniformity?

Only dominant alleles are expressed in the F1 generation

Traits blend in the F1 generation

All offspring in the F1 generation are homozygous

The characteristics do not blend and can reappear in later generations (correct)

What is the principle behind the Law of Independent Assortment?

The genes controlling different traits are inherited independently (correct)

The distribution of one pair of alleles influences the distribution of another pair

Autosomal dominant traits are always expressed

Sex-linked traits are always recessive

How many human traits or disorders are known to follow Mendelian principles?

Over 50,000

Over 5,000

Over 16,000 (correct)

Over 1,000

What is the characteristic of the ABO blood system?

Codominant inheritance Signup and view all the answers

What determines the type of Mendelian inheritance?

The chromosomal location of the gene locus Signup and view all the answers

What is the probability of a child inheriting an autosomal dominant trait from an affected parent?

1 in 2 (50%) Signup and view all the answers

What is the requirement for a recessive trait to manifest?

Two copies of the mutant allele Signup and view all the answers

What is the characteristic of an autosomal recessive disorder?

It is never expressed in heterozygotes Signup and view all the answers

What is the reason for X-linked recessive traits not being clinically manifested in females?

Because the normal copy of the gene is present Signup and view all the answers

Why are men more likely to be affected by X-linked recessive diseases?

Because they have only one X chromosome Signup and view all the answers

What is the characteristic of a Y-linked gene?

It manifests in all men carrying it Signup and view all the answers

What is the purpose of a Punnett square?

To predict the genotypes and phenotypes of offspring Signup and view all the answers

What is the first step in using a Punnett square?

Determine the genotypes of the parent organisms Signup and view all the answers

What is the characteristic of an X-linked recessive trait in women?

They are only affected if they are homozygous for the mutant allele Signup and view all the answers

What is the inheritance pattern of a Y-linked gene?

Only from father to son Signup and view all the answers

What is hypertrichosis of the ear?

A Y-linked gene that determines the appearance of hair on the pinna Signup and view all the answers

What is the ratio of smooth to rough peas in the F2 offspring?

3:1 Signup and view all the answers

What is the term Mendel used to describe the units of inheritance?

Gametes Signup and view all the answers

What is the result of multiplying two 3:1 ratios in a dihybrid cross?

9:3:3:1 Signup and view all the answers

What is the condition for a recessive allele to be expressed?

Two copies of the allele are required Signup and view all the answers

What is the term for the alleles that can be expressed in the presence of another allele?

Dominant Signup and view all the answers

What happens to the gene pairs during gamete production?

They separate Signup and view all the answers

What is the term for an individual with two identical alleles at the same locus?

Homozygous Signup and view all the answers

What is the law that states genes occur in pairs and separate during gamete production?

Law of Segregation Signup and view all the answers

Study Notes

Laws of Inheritance

Law of Uniformity: When two homozygotes with different alleles are crossed, all offspring in the F1 generation are identical and heterozygous.
Law of Independent Assortment: The distribution of one pair of alleles into gametes does not influence the distribution of another pair; genes controlling different traits are inherited independently.

Mendelian Inheritance in Humans

Mendelian principles apply to over 16,000 human traits or disorders.
The human ABO blood system is an example of a simple Mendelian inheritance:
- A and B alleles are dominant to the O allele.
- A or B alleles are codominant (both traits are expressed).

Types of Mendelian Inheritance

Autosomal dominant: A trait or disorder that manifests in the heterozygous state; 1 in 2 (50%) chance of inheriting it and being similarly affected.
Autosomal recessive: A trait or disorder that manifests only when the mutant allele is present in a double dose (homozygosity); individuals heterozygous for the mutant allele are healthy.
X-linked recessive: A trait that is not clinically manifested when a normal copy of the gene is present; fully evident in men, but women are rarely affected unless homozygous for the mutant allele.
Y-linked inheritance: Few genes are involved in primary sex determination or development of secondary male characteristics; a Y-linked gene will manifest in all men carrying it, regardless of dominance or recessiveness.

Punnett Square

Used to predict genotypes and phenotypes of offspring.
Steps:
1. Determine parent genotypes.
2. Write down the cross (mating).
3. Draw a Punnett square.
4. "Split" letters of the genotype for each parent and put them outside the square.
5. Determine possible genotypes of the offspring by filling in the square.

Dihybrid Cross

Analyzes two characters simultaneously.
Plants used as parental lines produced smooth yellow seeds and wrinkled green seeds.
Ratios obtained: 9:3:3:1, resulting from multiplying two 3:1 ratios (one for color and one for form).

Dominance and Recessiveness

Recessive traits are not expressed in heterozygotes; two copies of the allele are required for expression.
Dominant traits are governed by an allele that can be expressed in the presence of another, different allele; dominant alleles prevent expression of recessive alleles in heterozygotes.

Law of Segregation

Genes occur in pairs (like chromosomes).
During gamete production, members of each gene pair separate.
During fertilization, the full number of chromosomes is restored (allele pairs are reunited).
Homozygous: same allele at the same locus on both members of a chromosome pair (e.g., TT, tt).
Heterozygous: two different alleles at the same locus on a chromosome pair.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Quiz on Mendel's laws, including the Law of Uniformity and the Law of Independent Assortment, which describe how alleles are inherited and expressed in offspring.