3.4 INHERITANCE Flashcards
GENOTYPE
the combination of alleles of a gene carried by an organism
PHENOTYPE
the expression of alleles of a gene carried by an organism
HOMOZYGOUS DOMINANT
two copies of the same dominant gene (capital letter AA)
HOMOZYGOUS RECESSIVE
two copies of the same recessive gene (lowercase aa)
HETEROZYGOUS
two different alleles (one dominant, one recessive) (Aa)
CODOMINANT
pairs of alleles which are both expressed when present
CARRIER
an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele.
TEST CROSS
Testing a suspected heterozygote by crossing it with a known homozygous recessive.
MENDEL’S PEA PLANTS
Mendel performed experiments on a variety of different pea plants, crossing these varieties by using the male pollen from one variety and transferring it to the female part of another variety
He collected the seeds and grew them to determine their characteristics
He then crossed these offspring with each other and also grew their seeds to determine their characteristics
He continued performing many crosses and recorded his results.
MENDEL
father of genetics
GAMETES
sex cells such as sperm and eggs
GAMETES AND CHROMOSOMES
have only one chromosome of each type, gametes also only contain one allele of each gene
TWO GAMETES FORM
a zygote
WHEN GAMETES FUSE
to form a zygote (2n),
two copies of each gene exist in the diploid zygote
ZYGOTE MAY CONTAIN
Two of the same allele AA or aa or two different alleles such as Aa
MONOHYBRID CROSSING
Cross using a Punnett square
F1 generation genotype ratio is 1:2:1 and phenotype ratio is 3:1
ABO BLOOD GROUP
Human blood types are an example of both multiple alleles (A, B, O) and co-dominance (A and B are co-dominant).
ABO AND ANTIGEN
A, B and O alleles all produce a basic antigen (glycoprotein) on the surface of the red blood cells
A BLOOD GROUP AND ANTIGENS
They contain anti-B antibodies and antigen A, which are able to kill B and AB type blood.
A blood group people can accept A and O type blood but not the AB and B type.
B BLOOD GROUP AND ANTIGEN
possess anti-A antibodies and antigen B, which are able to kill A and AB type blood.
B blood group people can accept B and O type blood but not the AB and A type.
AB BLOOD GROUP AND ANTIGEN
possess NO antibodies and antigen A&B.
AB blood group people can accept ALL type of blood.
O BLOOD GROUP ANTIGEN
possess anti-A & anti-B antibodies and NO antigens, which are able to kill A, B and AB type blood.
O blood
group people can accept O type blood but not the A, AB and B type
UNIVERSAL RECEIVER
AB blood group
UNIVERSAL DONOR
O group
CYSTIC FIBROSIS
autosomal recessive disease caused by an allele of the CFTR gene on chromosome 7
CYSTIC FIBROSIS MUTATION
Mutation in the CFTR gene causes secretion of mucus to become very thick. Thick mucus blocks the airway tubes especially in lungs
CYSTIC FIBROSIS CONSEQUENCES
Cystic fibrosis patient dies young, around the age of 35-50
HUNTINGTON’S DISEASE LOCATION
Humans have two copies of the Huntingtin gene (HTT) on chromosome 4, which codes for the protein Huntingtin (Htt)
HUNTINGTON’S DISEASE
is dominantly inherited.
neurodegenerative genetic disorder
HUNTINGTON’S DISEASE CONSEQUENCES
affects muscle coordination and leads to mental decline and behavioral
symptoms
brain disorder, affecting the ability to think, talk and move.
SEX LINKAGE
These are patterns of inheritance where the ratios are different in males and females because the gene is located on the sex chromosomes
SEX LINKED DISEASES
X chromosomes
SEX LINKED TRAITS
carried on the X chromosomes non-homologous region.
NORMAL GENES
expressed in X domninant
ABNORMAL GENES
expressed in X recessive
X LINKED RECESSIVE DISEASES ARE MORE COMMON IN
males because males only carry one X
chromosome, therefore if they inherit the X chromosome with the disease, they will have the disease
EXAMPLES OF SEX LINKED RECESSIVE DISEASES
colour blindness and hemophilia
MALES AND X LINKED RECESSIVE DISEASE CAN ONLY
pass the colorblind or hemophilia allele onto their daughters. Their sons will receive the Y
chromosome.
RED- GREEN COLOUR BLINDNESS
Red-green blindness genes are recessive on the non-homologous region of X
So it is a sex-linked disease.
Patient’s retinal pigment will lose certain frequency so the cannot distinguish between red and green
HEMOPHILIA
Globular protein called clotting factor is needed to clot the blood.
A mutation will cause clotting factor not to work.
Clotting response to injury does not work: patient may bleed to death.
RADIATION EFFECTS
A mutation is a random change to the base sequence of a gene
Both radiation and certain chemicals can cause genetic diseases and cancer
Radiation can cause mutations if it has enough energy to chemical change one’s DNA. Gamma rays and alpha particles from radioactive
decay, UV radiation and x-rays are all considered to be mutagenic
Nuclear bombing of Hiroshima and accident at Chernobyl leads to high cancer rate
MUTAGENS
are agents that cause gene mutation such as chemicals, high energy radiation, ultraviolet light and some virus
ONCOGENES
genes that control the cell cycle and cell division
IF MUTATION OCCURS ON ONCOGENES
it may lead to cancer
MUTATION IN ONCOGENE
will lead to malfunction in control of the cell cycle, leading to uncontrolled cell division and cancer
MUTATIONS AND GAMETES
Mutation occurs in somatic cells will remain in the organism, but if it occurs in gametes, it will be passed on for generations
