Lesson 2 Flashcards by Kyra Catedral

is a unit of inheritance that encodes a particular protein, which is a key component of the human body

gene

How well did you know this?

Not at all

Perfectly

Proteins from Genes
• ____(triplets of nitrogenous bases) code for specific amino acids.
• Amino acids link together to form____.

Codons

proteins

How well did you know this?

Not at all

Perfectly

DNA and Chromosomes
• Genes are located in_____
• A double-stranded helix containing codons responsible for protein coding.

•	\_\_\_\_: Coiled DNA structures found in the nucleus, containing 23 pairs: (2)

DNA

Chromosomes

•	1 pair of sex chromosomes (XX or XY)
•	22 pairs of autosomes

How well did you know this?

Not at all

Perfectly

• control metabolic processes within the cell, affecting tissues, organs, and body systems.

Chromosomes

How well did you know this?

Not at all

Perfectly

Nitrogenous Bases
• (4)
• 3 consecutive nitrogenous bases
=____ (carries a specific amino acid).

• Amino acids link via _____to form proteins.

Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

1 codon

peptide bonds

How well did you know this?

Not at all

Perfectly

• Example: If a person has blood type A, their red blood cells express A antigens.

Phenotype

How well did you know this?

Not at all

Perfectly

• The outward expression of genes.
• A result of genotype expression.

Phenotype

How well did you know this?

Not at all

Perfectly

• The genetic makeup responsible for gene expression.

Genotype

How well did you know this?

Not at all

Perfectly

Example Scenario:
• An individual with blood type B has B antigens on red blood cells.
• Possible genotypes: ???

• BB (homozygous)
• BO (heterozygous) → One dominant (B) and one recessive (O) gene.

How well did you know this?

Not at all

Perfectly

T or F. Why??

• Two individuals can have the same phenotype but different genotypes.

• One could be homozygous (AA or BB).
• The other could be heterozygous (AO or BO).

• A & B are dominant genes → Antigens are expressed when present.

How well did you know this?

Not at all

Perfectly

Genetic Principles in Blood Banking

Inheritance of Blood Type
• If both parents are heterozygous (AO and BO), their offspring can inherit different combinations of these genes.
• Possible genotypes for the offspring:????
• OO is…
• AB, AO, and BO are…

AB, AO, BO, OO.

homozygous (recessive)

heterozygous

How well did you know this?

Not at all

Perfectly

Phenotype is determined by the____ expressed on red blood cells.

• A and B genes are dominant, so when both are present, both antigens are expressed →____

antigens

Type AB blood

How well did you know this?

Not at all

Perfectly

Important tool for illustrating the probability of genotypes from known or inferred genotypes

Punnett square

How well did you know this?

Not at all

Perfectly

• _____are located at specific____ (positions) on chromosomes.

• Example: ABO blood group gene is found on chromosome____.

Genes

loci

How well did you know this?

Not at all

Perfectly

• Different forms of a gene at a specific locus.

Alleles

How well did you know this?

Not at all

Perfectly

• ABO alleles:

• Each locus can only contain____ allele from each parent.

A, B, and O.

one

How well did you know this?

Not at all

Perfectly

Blood Group System

ABO
Rh
Diego

Chromosome????

9 ABO
1 Rh
17 Diego

How well did you know this?

Not at all

Perfectly

Antithetical

Allelic genes are_____, meaning only one form can be present at a given locus.

• Example: A, B, and O alleles—…

antithetical

each person inherits only one from each parent (either A B or O)

How well did you know this?

Not at all

Perfectly

• Genes with multiple alleles at a single locus.

Polymorphic Genes

How well did you know this?

Not at all

Perfectly

Polymorphic Genes

• Example:
• Rh blood group _____ alleles
• HLA (Human Leukocyte Antigen) has extensive variation, making organ matching difficult.

has 5 alleles (D, C, c, E, e).

How well did you know this?

Not at all

Perfectly

Inheritance patterns: (3)

Codominant
Dominant
Recessive

How well did you know this?

Not at all

Perfectly

Both inherited dominant genes are expressed.

AB blood type (both A and B antigens are expressed).

Codominant

How well did you know this?

Not at all

Perfectly

A single dominant gene expresses its trait, even if paired with a recessive gene.
A or B blood type (AO or BO genotype).

Dominant

How well did you know this?

Not at all

Perfectly

A recessive gene is only expressed if inherited in a homozygous state.

O blood type (OO genotype).

Recessive

How well did you know this?

Not at all

Perfectly

Key Summary • Dominant (A/B) + Recessive (O) →… • Both Dominant (A & B) →… • Both Recessive (O & O) →…

Antigen is expressed (Type A or B) Both antigens are expressed (Type AB) No antigen expression (Type O)

do not code for any functional product (e.g., antigens).

Silent, amorph, or null genes

Silent, amorph, or null genes Causes (2)

1. ***Inheritance of an amorphic gene from both parents*** (homozygous for a non-functional gene). 2. ***Action of suppressor genes*** that inhibit gene expression, even if a dominant gene is present.

Example Scenario • A person inherits a dominant gene (e.g., Lu^a/Lu^b for the Lutheran blood group), • However, if a suppressor gene (In^Lu) is present, no antigen will be expressed, leading to a null phenotype (Lu a-b-).

Silent, Amorph, and Null Genes

There will be instances where despite inheriting a dominant gene, the inheritance of a suppressor gene will inhibit the expression of the products of a gene, regardless of inheriting dominant genes = product of genes will not be expressed Lutheran: Dominant Suppresor

Dominant gene: ***Lu a/Lu b*** Suppressor gene: : ***In(Lu)***

The amorph phenotype of the ABO blood group system

Null phenotype of Rh blood group ***Does not allow the expression of DCcEe antigens***

Rh null

Null phenotype From the inheritance of both the recessive genes of the Lutheran blood group

Lu (a-b-)

are located at specific loci (positions) on chromosomes.

Genes

• Different forms of a gene at a specific locus.

Alleles

ABO alleles:

A, B, and O.

Allelic genes are______, meaning only one form can be present at a given locus. • Example: A, B, and O alleles—each person inherits only one from each parent.

antithetical

• Genes with multiple alleles at a single locus. • Example: • Rh blood group has 5 alleles (D, C, c, E, e). • HLA (Human Leukocyte Antigen) has extensive variation, making organ matching difficult.

Polymorphic Genes

Inheritance of an _______ gene from both parents (homozygous for a non-functional gene).

amorphic gene

Action of______ genes that inhibit gene expression, even if a dominant gene is present.

suppressor genes

• A person inherits a dominant gene (e.g., Lu^a/Lu^b for the Lutheran blood group), • However, if a suppressor gene (_____) is present, no antigen will be expressed, leading to a null phenotype (Lu a-b-).

In^Lu

Kell Amorph Phenotype

K° (Silent Kell gene) Kell-null (K0K0)

Lutheran Amorph Suppressor Phenotype

Lu (Amorph Lutheran) In(Lu) Lu(a-b-)

Lutheran Amorph Suppressor Phenotype

Lu (Amorph Lutheran) In(Lu) Lu(a-b-)

Kidd Amorph Suppressor Phenotype

Jk In(Jk) Jk(a-b-)

Duffy Amorph Phenotype

Fy Fy(a-b-)

ABO Amorph Phenotype

O O

H Amorph Phenotype

h Bombay

Bombay Phenotype

(hh)

Suppressor Genes in Blood Groups: • → Even if dominant genes are present, these suppressor genes prevent antigen expression.

Lutheran (In^Lu) and Kidd (In^Jk)

Mendelian Principles in Blood Group Inheritance

1. Independent Segregation (Law of Segregation) 2. Independent Assortment (Law of Independent Assortment)

• Each parent has two copies of a gene but can ***pass only one allele to their offspring.*** • The Punnett square demonstrates how each gene is transmitted independently.

Independent Segregation (Law of Segregation)

• ***Genes for different traits are inherited separately*** when located on different chromosomes.

Independent Assortment (Law of Independent Assortment)

ABO Chromosome

Kell Chromosome

Rh Duffy

Lutheran Lewis LW Hh Chromosome

• _____genes do not produce any antigen → Leads to null phenotypes. • _____genes inhibit antigen expression, even if a dominant gene is inherited.

Amorph (null) Suppressor

Mendelian inheritance explains how blood group antigens are inherited: • Independent segregation →______ • Independent assortment →_____

One allele from each parent. Blood group genes on different chromosomes are inherited separately.

Understanding heterozygosity and homozygosity is crucial in blood banking because it affects the_______, which influences the strength of antigen-antibody reactions in serological testing.

dosage effect

Homozygous for Jk^a (Jk(a+b-)) Reaction Strength:

Strong (3+) • Why? Because there is a double dose of Jk^a antigens, many antibodies can bind, leading to stronger hemagglutination.

Heterozygous for Jk^a and Jk^b (Jk(a+b+)) Reaction Strength:

Weaker (1+ to 2+) • Why? Because the red cells contain both Jk^a and Jk^b antigens, there are fewer Jk^a antigen sites for the antibodies to bind, resulting in a weaker reaction.

• _____individuals have a mixed antigen population, leading to weaker serological reactions (1+ to 2+). • _____individuals have a double dose of antigens, leading to stronger reactions (3+). • Blood group antibodies can show dosage effects, meaning they react more strongly with ***homozygous cells*** than heterozygous cells.

Heterozygous Homozygous

These concepts explain exceptions to Mendel’s Law of Independent Assortment, particularly when genes are located close to each other on the same chromosome.

Linkage, Haplotypes, and Crossing Over

are genes that are close together on the same chromosome and tend to be inherited together rather than independently. • Example: MNSs blood group system

Linked genes

A_______ is the ***genetic combination of linked genes*** that are inherited as a unit. • In the MNSs system, possible haplotypes are MS, Ms, NS, Ns instead of individual inheritance of M, N, S, and s separately.

haplotype

• Definition: When certain haplotypes occur more frequently in a population than expected by chance. • Example: If genes were inherited separately: • M = 17% of population • S = 12% of population • However, because M and S are linked, the MS haplotype might be found in 24% of the population instead of the expected (17% × 12% = 2%).

Linkage Disequilibrium

Crossing Over • Occurs during cell division

(Prophase I of Meiosis)

• Exchange of genetic material between homologous chromosomes, leading to genetic recombination. • Result: Creates genetic variation, making individuals unique—even identical twins!

Crossing over

close together on a chromosome are inherited together MNSs blood group

Linkage Genes

Combination of linked genes that are inherited as a unit MS, Ms, NS, Ns

Haplotype

When certain haplotypes appear more frequently than expected by chance MS occurring in 24% instead of 2%

Linkage Disequilibrium

Calculations This process is used to determine the ***frequency of a particular phenotype in a population,*** helping to find compatible donor blood units for transfusion, ensuring that they lack certain antigens that could cause hemolytic transfusion reactions.

Combined Phenotypic Calculations

Gene Frequencies:

Hardy-Weinberg Equations

Hardy-Weinberg Formula

p^2 + 2pq + q^2 = 1

Hardy-Weinberg Formula p^2 + 2pq + q^2 = 1 Where: • ___= frequency of the dominant allele (homozygous) • ___= frequency of the recessive allele (homozygous) • ___= heterozygous genotype (combination of dominant and recessive alleles) Also, it’s known that: p + q = 1

p q pq

No longer appliacble In the past, methods like blood typing were used for paternity testing to determine biological relationships. However, with advancements in DNA testing and molecular genetics, these older methods have become less reliable. Today, DNA testing is the most accurate way to confirm or exclude paternity.

Relationship Testing

Paternity Testing Methods:

DNA testing Blood typing

• Uses polymerase chain reaction (PCR) and other molecular genetics techniques to analyze genetic material and confirm or disprove paternity.

DNA Testing (Molecular Studies)

• Screening Test: Provides clues about paternity but is not a confirmatory test.

Blood Typing

Types of Paternity Testing:

1. Direct Exclusion 2. Indirect Exclusion

DE and ID are both dependent on the _____ gene

Obligatory gene - expected to be passed on to the baby

• Definition: When the child’s genetic marker is absent from both parents.

Direct Exclusion

Example: • Mother: Blood type O (OO genotype) • Father: Blood type A (AA or AO genotype) • Child: Blood type B (BO genotype) • Explanation: The B marker in the child cannot be passed on by either parent (because the parents do not have the B allele), so______ occurs. This means the man cannot be the biological father.

direct exclusion

• Definition: When only one parent has the genetic marker, but the result might be influenced by other genetic factors (like a suppressor gene).

Indirect Exclusion

Example (using Kidd Blood Group system): • Mother: Jk (a+b-) — Genotype: Jkª/Jka • Father: Jk (a-b+) — Genotype: Jk’/Jkº • Child: Jk (a+b-) — Genotype: Jkª/Jkº • Explanation: The child’s blood type suggests the father should have passed on a Jk’ gene. However, if the father has a suppressor gene that inhibits the expression of the Jk’ antigen, the absence of Jk’ on the father’s side does not necessarily exclude him as the father. This is termed______, as the suppressor gene could explain the lack of Jk’ expression.

Indirect Exclusion