Mendelian Inheritance Flashcards
What did Mendel use to discovers mendelian inheritance?
Peas, and flowers
What did it prove when the F2 generation gave rise to white flowers, even though the F1 generation only had white flowers?
Showed the gene was carried through the generations, and that inheritance isn’t blending
What are menders laws?
Law of segregation
Law of independent assortment
What is the law of segregation
Two members from each other during the formation of gametes - half of the gamete carry one member of the pair, the other half carry the other member of the pair
What is the particulate mechanism?
Parents pass on discrete heritable units - genes
How do you calculate the ratios of two characters at the same time?
Law of multiplication
What is the principle of independent assortment?
Alleles of different genes segregate independently of each other
When might you see two characters passed on together?
When they occur at physically proximate chromosomes - linked genes, so don’t assort independently
Why iOS mendelian inheritance needed for natutral selection?
Natural selection works because:
Individuals vary genetically
Some variants are fitter than others
Variation is heritable
What would occur if blending inheritance was possible?
All individuals would become the same
What is a monogenic disease?
One gene is involved
What is a multi factor disease?
Many genes are involved
How many mendelian characters are detected in man?
6000+
How is a disease on a recessive gene inherited
Affected individual has inherited it from both parents
What is and autosomal disease?
Caused by a gene on chromosomes 1-22
What are the characteristics of an autosomal dominant disease?
Affected person usually has at least one affected parent
Affects either sex
Transmitted by either sex
What is the chance of an autosomal dominant disease being inherited by offspring with one affected and one unaffected parent?
50% - Affected parent has to be heterozygous
What are some examples of diseases and conditions caused by autosomal dominance?
Achondroplasia – a form of dwarfism Polydactyly – extra fingers or toes Hairy mid-digit
Widow’s peak
What a are the characters of Autosomal recessive diseases?
Patient is homozygous recessive if affected
Heterozygous are carriers
Affected usually have unaffected parents
Parents are both carriers
Affects either sex
Result of increased incidence of inbreeding
Carriers and non carriers are indistinguishable
What are the chances of offspring of two carriers being a carrier and being affected
Carrier = 1/2 affected = 1/4
What are some examples of autosomal recessive diseases?
Albinism
Sickle cell anemia
cystic fibrosis
Attached earlobes
What is cystic fibrosis?
Affects the lungs, increased mucus secretion is caused by mutated copies of the CTRF gene - homozygous are affected. There is a 3bp deletion leading to a non functional protein
How may being a carrier of the cystic fibrosis gene be beneficial?
May have or had an advantage through reactance to certain diseases, such as cholera and typhoid, but no symptoms shown
What are the characteristics of X Linked recessive diseases?
2/5 male offspring of female carriers are affected
Males can’t be carriers - are affected if the recessive is present
0/5 female offspring of female carriers are affected
3/5 female offspring are carriers
