Genetics: Multiple Alleles

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Questions and Answers

What is the maximum number of alleles an individual can possess at a gene locus?

Two (correct)

Three

Any number

One

What is the process by which genes can change to alternative forms?

Natural selection

Gene expression

Genetic drift

Mutation (correct)

What is the typical approach to teaching genetics?

Using only real-world examples

Using a combination of simple and complicated genetic situations

Using the most complicated genetic situations

Using the simplest possible genetic situations (correct)

What is the relationship between the number of alleles and the complexity of gene interactions?

The more alleles, the more complex the gene interactions Signup and view all the answers

What is the result of a single pair of alleles in a genetic system?

A limited genetic system Signup and view all the answers

What is the theoretical possibility of alleles in a population of individuals?

A large number of alleles Signup and view all the answers

What is the term used to describe a gene locus in a population with more than two alleles?

Multiple alleles Signup and view all the answers

How many alleles are present in the ABO blood group gene?

3 Signup and view all the answers

What is the number of possible genotypes for a gene with three alleles?

6 Signup and view all the answers

What is the relationship between the number of alleles and the number of possible genotypes?

The number of possible genotypes is proportional to the square of the number of alleles Signup and view all the answers

What is the symbol used to represent the dominant allele in a multiple allele system?

Capital letter Signup and view all the answers

What is the term used to describe the hierarchy of dominance among multiple alleles?

Dominance hierarchy Signup and view all the answers

How many alleles can be present in any one diploid organism?

2 Signup and view all the answers

What is the formula used to calculate the number of possible genotypes for a gene with n alleles?

$n(n+1)/2$ Signup and view all the answers

What is the number of possible genotypes for a gene with 4 alleles?

10 Signup and view all the answers

What is the relationship between the number of alleles and the number of possible phenotypes?

There is no fixed relationship between the number of alleles and the number of possible phenotypes Signup and view all the answers

What is the term for a molecule that triggers an immune response in the body?

Antigen Signup and view all the answers

What is the genotype of an individual with ABO blood type AB?

IA IB Signup and view all the answers

Why is it essential to cross-match blood types before transfusion?

To prevent agglutination or clumping of cells Signup and view all the answers

What is the function of glycosyltransferases in the ABO blood type system?

They specify the type of glycolipids found on the surface of erythrocytes Signup and view all the answers

Which of the following ABO blood type combinations is NOT possible?

AA Signup and view all the answers

What is the term for a protein produced by the immune system in response to the presence of an antigen?

Antibody Signup and view all the answers

Which of the following is a practical application of knowledge on ABO blood types?

Blood transfusions Signup and view all the answers

Which of the following is NOT a phenotype resulting from the mating A x O?

AB Signup and view all the answers

What is the genotype of an individual with ABO blood type O?

IO IO Signup and view all the answers

In the case described in question 1, what can be concluded about the man's paternity of the child?

He is not the father Signup and view all the answers

What can be inferred from a child's blood type if it is different from the mother's blood type?

The child is not the biological child of the mother. Signup and view all the answers

What is the probability of a child having Type O blood if the parents are both heterozygous for the 'B' blood type?

25% Signup and view all the answers

What is the RhD factor?

A protein found on the surface of red blood cells. Signup and view all the answers

What is the significance of the RhD factor in pregnancy?

It can cause an immune response in the mother. Signup and view all the answers

What is the term for the complication of pregnancy caused by the RhD factor?

Rh (D) disease Signup and view all the answers

What is the probability of an RhD- mother conceiving an RhD+ baby if the father is RhD+?

50% Signup and view all the answers

What is the genotype of a person who is Type A and Rh+?

AA or AO Signup and view all the answers

What is the purpose of the Anti-D antibodies in the mother's immune system?

To attack the RhD+ blood cells of the baby Signup and view all the answers

What is the significance of the ABO blood type system?

It determines the blood type of an individual. Signup and view all the answers

What is the term for the antibodies produced by the mother's immune system against the RhD+ blood cells?

Anti-D antibodies Signup and view all the answers

Study Notes

Introduction to Multiple Alleles

The genetic systems proposed so far have been limited to a single pair of alleles.
An individual possesses a maximum of two alleles at a gene locus, one on each of the homologous chromosomes.
Genes can change to alternative forms through the process of mutation, making a large number of alleles theoretically possible in a population.

Characteristics of Multiple Alleles

Multiple alleles occur when more than two alleles are identified at a gene locus in a population.
Each individual has only two alleles for a particular trait, despite the presence of multiple alleles in the population.
The presence of multiple alleles increases the number of possible genotypes among diploid organisms.

ABO Blood Group Example

The ABO blood group gene has three alleles: A, B, and O.
Each individual has only two alleles for the ABO blood group gene, resulting in six possible genotypes: AA, AB, AO, BB, BO, and OO.
These six genotypes produce four possible phenotypes: A, B, AB, and O.

Calculating the Number of Genotypes

The number of possible genotypes is a function of the number of alleles that exist for a given gene.
The formula to calculate the number of genotypes is: 𝐧(𝐧 + 𝟏) / 𝟐, where n is the number of alleles.

Dominance Hierarchy

The dominance hierarchy should be defined at the beginning of each problem involving multiple alleles.
A capital letter is used to designate the allele that is dominant, while a lower-case letter designates the allele that is recessive to all others in the series.### Symbols for Multiple Alleles
The dominance hierarchy: capital letters for dominant alleles and lower case letters for recessive alleles
Example: Coat Color in Rabbits
- Four alleles of the rabbit coat color (c) gene have been studied
- Alleles: C (wild-type), cch (Chinchilla), ch (Himalayan), and c (Albino)
- Gradation in dominance: C > cch > ch > c
- Dominant allele: C
- Recessive alleles: cch, ch, and c

ABO Blood Type Alleles in Humans

One of the most firmly established series of multiple alleles in humans involves the genetic locus controlling the blood types, A, B, and O
Three alleles: I (A), I (B), and i (O)
ABO blood group system:
- Type A: I and i alleles
- Type B: I and i alleles
- Type AB: I and I alleles
- Type O: i allele
Antigens and antibodies:
- A antigen: found on the surface of red blood cells of type A individuals
- B antigen: found on the surface of red blood cells of type B individuals
- Anti-A antibody: produced by type B and type O individuals in response to A antigen
- Anti-B antibody: produced by type A and type O individuals in response to B antigen
ABO blood type inheritance:
- IAIO heterozygous individuals have A and B antigens on their red blood cells
- IOIO homozygous individuals have no ABO antigens on their red blood cells

Blood Transfusion Compatibility for the ABO Blood Groups

Compatible blood transfusions:
- Type O blood can be transfused to individuals of any blood type
- Type AB blood can receive blood from individuals of any blood type
Incompatible blood transfusions:
- Type A blood cannot be transfused to type B or type O individuals
- Type B blood cannot be transfused to type A or type O individuals
- Type AB blood cannot be transfused to type A, type B, or type O individuals

Applications of Knowledge on Blood Types

Blood transfusions: compatible blood transfusions can be achieved by matching the ABO blood types of the donor and recipient
Disputed parentage: decisions of disputed parentage can be accurately made by examining the ABO phenotypes of the possible parents and the child### Blood Type and Rh Factor
The blood type of a person is determined by the genes inherited from their mother and father.
There are four main blood types: A, B, AB, and O, each with a positive (RhD+) or negative (RhD-) Rh factor.

Rh Factor

The RhD (Rhesus) factor is a protein that is either present (RhD+) or absent (RhD-) on the surface of a person's red blood cells.
A person's Rh factor is determined by their genotype, with RhD+ being dominant and RhD- being recessive.

Rh Factor Status

An individual is either Rh positive (Rh+) if they have the D antigen or Rh negative (Rh-) if they do not.
The Rh factor is important in blood transfusions and pregnancy, as an Rh- individual may have an immune response to RhD+ blood cells.

Blood Type Inheritance

The possible blood types of a child depend on the blood types of their parents.
For example, if both parents are heterozygous for the "B" blood type, the possible blood types of their child are BB, BO, or OO.

Paternity and Blood Type

Blood type information can be used to determine paternity in certain cases.
For example, if a woman with blood type AB claims a child with blood type O, the biological father cannot be a man with blood type A.

Hemolytic Disease of the Newborn (HDN)

HDN, also known as 'Rh (D) disease', occurs when an RhD- mother has anti-D antibodies that attack her unborn RhD+ baby's red blood cells.
This can happen if the mother has had a previous pregnancy with an RhD+ baby or has had a blood transfusion with RhD+ blood.

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Description

This quiz covers the concept of multiple alleles in genetics, including the characteristics and implications of having more than two alleles at a gene locus.