Mendel's law and patterns of inheritance

Question 1

what are the main points of Mendel experiments?

Answer 1

1) A trait might not show in an individual but still be shown in the next generation

2) Law of segregation (a unit is inherited from each parent for each trait)

3) Law of independent assortment (separate genes for separate traits are inherited independently from parents)

Question 2

what are the modes of inheritance proposed by mendelian?

Answer 2

1) Autosomal Dominant
2) Autosomal recessive
3) X-Linked dominant
4) X-Linked recessive

Question 3

What is the meaning of congenital disorder?

Answer 3

defects in the developing fetus (Not necessarily genetic, like environmental “Radiation”)

Question 4

What is the meaning of Genetic disorders?

Answer 4

disordered that are due to defective genes

Question 5

What is the meaning of genotype?

Answer 5

The genetic constitution of genes

Question 6

What is the meaning of phenotype?

Answer 6

it is the observed expression of a genotype

Question 7

What is the meaning of genetic locus?

Answer 7

The specific position of each gene on the chromosomes

Question 8

What is an allele?

Answer 8

Chromosomes are formed of two arms called chromatids, alleles are the genetic sequence in certain loci in the chromatids, they have the sequence of nucleotide that makes up each trait in the body (2 alleles for each trait one from the mother and the other from the father)

The dominant allele is represented by a capital letter

recessive by small letters

In their genotype they can be:

1) Homozygote: Both alleles are the same (DD)
2) Heterozygote: alleles are different (Dd)
3) Hemizygote: Only one allele of a trait like the sex trait in males (X from mother & Y from father)

If two alleles are coding for the same trait it can have no effect (Blood group “AB”) or cause genetic disorders (Cystic fibrosis & hemophilia)

Question 9

What are the different types of genetic disorders?

Answer 9

1) Mendelian inheritance-Single-Gene-Defect:
- Autosomal Recessive
- Autosomal Dominant
- X-Linked Recessive
- X-Linked Dominant

2) Chromosomal Disorders:
- Numerical Abnormalities
- Structural Abnormalities

3) Multifactorial Disorders
- Determined by one or more genes along with environmental factors

4) Mitochondrial disorders

Question 10

In a pedigree, offsprings are red from which direction?

Answer 10

From left to right

Question 11

In a pedigree, how is mating between relatives shown?

Answer 11

By two connecting lines

Question 12

What does a cross (X) represent in a pedigree?

Answer 12

That the person is dead

Question 13

with increased generations the chance of getting a disease increased or decreased?

Answer 13

Increased

Question 14

Explain the autosomal dominant disease inheritance?

Answer 14

• Both males & females are affected
• There is a person infected in each generation
• Every affected person has an affected parent
• Offsprings has a 50% risk of being affected
• Unaffected persons do not transmit the disease
  -Males & females can transmit the disease to males and females
• No carriers are present

Question 15

What are some examples of disease transmitted in a Autosomal dominant pattern?

Answer 15

1) Retinitis pigmentosa
2) Achondroplasia (child will have a short length in general, Short limbs “dwarfism in general”)
3) Osteogenesis Imperfecta (Bones will fracture easily)

Question 16

Why is people carrying the disease will have it in a heterozygote form?

Answer 16

Because if it were homozygote they would die on an early age (not hemi)

Question 17

How can you identify and autosomal pattern pedigree?

Answer 17

1) Affected child will have an affected parent
2) Both males and females are affected

Question 18

Describe the autosomal recessive inheritance pattern.

Answer 18

• Both males & females are affected
• People may not be affected in each generation
• An affected person might not have an affected parent
• Both parents must be carriers of the recessive gene
• 25% Risk of offspring having an inherited disease
• Inbreeding increases the risk (cousins marriage)

Question 19

list 6 Examples of diseases inherited in an autosomal recessive pattern

Answer 19

1) Galactosemia
2) Phenylketonuria (decrease in the metabolism of phenylalanine, which leads to intellectual disabilities, seizure, mental disorders, & behavioral issues, . A baby born to a mother who has poorly treated PKU may have heart problems, a small head, and low birth weight, must be away from starchy food potatoes and corn and many more)
3) Cystic fibrosis
4) Thalassemia major
5) Many forms of deafness
6) Sickle cell anemia

Question 20

How can you identify the pedigree of an autosomal recessive inheritance pattern?

Answer 20

• Affected children might have unaffected parents
• 25% Having the disease, 25% normal, 50% carrier
• Affects both males and females

Question 21

what is an example of an autosomal dominant trait?

Answer 21

Widows peak (Hair line)

Question 22

What is an example of an autosomal recessive trait?

Answer 22

Attached ear lobe

Question 23

What is an X-Linked recessive disorder?

Answer 23

• Usually, only males are affected
• There is no cases of male to male transmission
• All afected males can be linked to unaffected carrier females

Question 24

Examples of X-linked recessive diseases that are inherited

Answer 24

1) Haemophilia
2) Duchene muscular Dystrophy
3) Red-Green color blindness

Question 25

What is the meaning of autosomal?

Answer 25

genes located on non-sex chromosomes

Question 26

How to determine the pedigree of an X-linked recessive disorder?

Answer 26

• If the father is affected and the mother is a carrier then all females will be a carrier
• Males are either affected or not but never carriers
• Affected person might have parents that are not affected
• Not necessarily in every generation
• Only males are carriers

Question 27

What is the meaning of dominant inheritance?

Answer 27

When the trait (disorder) is expressed in the heterozygote (Dd)

Question 28

What is the meaning of recessive inheritance?

Answer 28

When the trait is only expressed in the homozygote (dd)

Question 29

what is the meaning of autosomal inheritance?

Answer 29

Genes on chromosomes 1-22

Question 30

what is the meaning of X-linked (sex-linked) inheritance?

Answer 30

Genes on the X (or Y) chromosomes

Question 31

What is meant by incomplete dominance?

Answer 31

where one allele is not dominant over the other resulting in a combined phenotype

• Like in Familial Hypercholesterolemia
  +/+ = normal
  +/- = death as young adult
  -/- = death in childhood
• Orange flower to a yellow and red parent

Question 32

What is meant by codominance?

Answer 32

it is when two alleles for the same gene are expressed, both traits appear

Like blood type AB, in addition to pigmented animals (The allele for the red and white color are both dominant in the parents, so the offspring will come representing both the colors in its geno and phenotype. ) and plants

Question 33

flip the card general info (summary)

Answer 33

In complete dominance, only one allele in the genotype is seen in the phenotype. In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.

Question 34

What is meant by expressivity?

Answer 34

It is the degree/severity of phenotype expression like baldness patterns in some of the offspring having this gene is shown extensively while others might have genes that suppress it, environmental factors also play a big role

Question 35

What is the meaning of pleiotropy?

Answer 35

it is when a gene influences the phenotype of more than one part of the body, the gene influencing the length of the left leg does the same to the right, they affect the connective tissue and are linked to Marfan syndrome (which Ibrahim lincoln and Osama bin laden had, which can cause heart valve prolapse “it is a connective tissue”)

Question 36

What is the meaning of penetrance?

Answer 36

It is a ratio of the number of individuals expressing the trait to the number of individuals carrying the trait

• Penetrance = number of individuals expressing trait/ number of individuals carrying the mutation I can be affected by environmental factors

Question 37

What is the meaning of genomic imprinting?

Answer 37

Different activation of a gene depending on whom it was inherited from

• when one of the alleles on the chromosomes from either the mother or father gets deleted
• Examples include: Prader-Willi Chr15 paternal deletion on the other hand Angelman syndrome chr15 deletion from the maternal chromosome
• Prader-Willi syndrome is a complex genetic condition that affects many parts of the body. In infancy, this condition is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. Beginning in childhood, affected individuals develop an insatiable appetite, which leads to chronic overeating (hyperphagia) and obesity. Some people with Prader-Willi syndrome, particularly those with obesity, also develop type 2 diabetes (the most common form of diabetes).
  -Angelman syndrome or Angelman’s syndrome (AS) is a genetic disorder that mainly affects the nervous system.[7] Symptoms include a small head and a specific facial appearance, severe intellectual disability, and developmental disability. Usually always happy and laughing like angels

Question 38

What are the features of mitochondrial DNA?

Answer 38

• Not a linear chromosome
• Similar to bacterial DNA
• Contains Genes for synthesis of rRNA (2), tRNA (22), 13 proteins in the electron transport chain that produces ATP

Question 39

How to identify the mitochondrial inheritance pedigree?

Answer 39

• All children of affected males WILL NOT inherit the disease.
• All children of affected females WILL inherit it.
• There are NO carriers
• Complicated by heteroplasmy (proportion of mitochondria with defective DNA)

Question 40

What is meant by heteroplasmy?

Answer 40

The mode of inheritance of mitochondrial pattern is through heteroplasmy which is the proportion of mitochondria with defective DNA.