Inheritance Flashcards
in summary what did Mendel observe
true-breeding pea plants
produced genetically identical offspring
tall produced tall and short produced short
true breeding plants self pollinate
what are menders 3 laws
law of segregation
law of independent assortment
principle of dominance
law of segregation
yeah individual possesses two units of inheritance for each characteristic
although only one of These is transmitted to each offspring
law of independent assortment
genes at different loci segregate independently
principle of dominance
in pairs of alleles that are different
one allele will mask the effect of the other allele
human traits to show mendelian inheritance
hitchhikers thumb
tongue rolling
attached earlobes
human earwax
consistency of earwax
SNP in ABCC11 gene is the determinant of human earwax type
mendelian genetics in inherited diseases
sickle cell disease
huntingtons
different ways genetic condition can be inherited
mutations in single gene and usually inherited in one of several patterns
autosomal dominant
one mutated copy of gene is sufficient for person to be affected by disorder
can inherit from affected parent
huntington disease and Marfan syndrome inheritance
may result from new mutation in gene and our in people with no history of disorder
loci are on an autosome
not X or Y chromosome
dominance being relative based
on the function of the protein and nature of the allele
incomplete dominance
where allele has partial effect over other allele
co-dominance
where both alleles are apparent
Huntingdons disease
neurodegenerative disorder caused by an allele that codes for a dominant phenotype
offspring have 50% chance of inheriting allele and therefore disease from a parent with the disease
autosomal reessive
both copies of the gene in each cell have mutations
parents of individual with autosomal recessive condition each carry one copy of the mutated gene but they typically don’t show signs or symptoms
typically not seen in every generation in a family
examples of autosomal recessive conditions
cystic fibrosis
sickle cell
sickle cell disease
blood disorder
RBCs distorted into sickle or crescent shape leading to premature breakdown or getting stuck in small blood vessels leading to anaemia
autosomal recessive
heterozygous carriers of sickle cell disease
express partial phenotype
some blood cells are normal and some distorted
only sometimes have moderate symptoms
full sickle cell disease
individual must have 2 copies of alleles coding or recessive phenotype
must be homozygous recessive
x linked dominant
loci are on X chromosome
allele masks other allele on other chromosome
x linked dominant in males vs females
males only require one copy of the gene to cause the disorder, often more severe
females require one of the two copies is sufficient
x linked recessive
XX females allele is masked by other allele on other chromosome unless both alleles are mutant
XX female has one normal and one mutant
doesn’t normally show any phenotype
XY males always affected
X- linked recessive disorders
one altered copy of gene in each cell is sufficient in males
in females mutation must occur in both copies of gene
example of x linked recessive disorders
haemophilia
fabry disease
fabry disease
inherited disorder that can affect many parts of the body
espeially heart and kidneys
have problems breaking down globotriaosylceramide (GL-3)
belongs to group of disorders known as lysosomal storage disorders
Y linked
XY males always affected
not many known conditions
200 genes on Y chromosome
only passed father to son
Y chromosome infertility
de novo mutations
caused by whole gene deletions in AZF region of Y chromosome responsible for sperm production
non-mendelian inheritance
where both alleles are expressed and influence the trait or genetic disease
ABO blood system
blood groups result from inheritance of alleles within a gene that can modify protein on red cells
3 alleles are ABO
O silent, A and B make different carbohydrate modifications
if they can’t make A or B then possess natural IgM antibodies against A and B proteins
major concern in blood transfusion
mitochondrial linked
loci are in mitochondrial DNA
distinct from mutations in nuclear DNA that affect mitochondria
passed mother to children exclusively
what is heritability
measure of how well differences in peoples genes account for differences in their traits
heritability as a statistical concept
h^2
describes how much of the variation in a given trait can be attributed to genetic variation
estimate of the heritability of a trait is specific to one population in one environment
can change as circumstances change
what do heritability estimates range from
0 to 1
0 indicates almost all variability is due to environmental factors, very little genetic difference influence
characteristics with heritability of 0
religion
language spoken
political preference
not under genetic control
phenylketonuria (PKU)
high heritability and most complex traits in people
including intelligence, multifactorial diseases
variability due to combination of genetic and environmental factors
despite knowing the heritability what do you not know
which genes or environmental influences are involved
or that if it is 0.7 doesn’t mean that 70% are caused by genetic factors its 70% of variability in trait is due to genetic differences
polygenic
combined affect of multiple genes
polygenic
combined affect of multiple genes
what are many health conditions caused by
polygenic
interactions between genes and environment
exampels of diseases caused by multiple genes/ gene environment
heart disease
type 2 diabetes
schizophrenia
certain cancers
label the image
label green pink and blue
green is homologous pair, homologs
diploid
pink= maternal homolog
blue= paternal homolog
what does each diploid human cell nucleus contain
2 similar versions of each autosome plus pair of sex chromosomes
46 chromosomes
maternal and paternal homologs/ homologous chromosomes
sexual reproduction is result of what
fusion of two gametes
including genetic material
need mechanism by which genetic material of precursor cell (gametes) is reduced by a half
meiosis
cell cycle and mitosis
Interphase: cellular components are replicated
G1 and G2: cell duplicates specific molecules and structures
S phase: cell replicates DNA
Mitosis: cell distributes its contents into two daughter cells
Interphase: chromosomes are uncondensed
Prophase: the spindle condenses, centrioles appear and the nuclear envelope breaks down
Metaphase: chromosomes align
Anaphase: centromeres and chromatids part
Telophase: spindle disassembles and nuclear envelope reforms
Two identical diploid daughter cells (2n)
meiosis 1 and 2
Prophase I (early): synapsis and crossing over occurs
Prophase I (late): chromosomes condense, become visible; spindle forms; nuclear envelope fragments; spindle fibres attach to chromosomes
Metaphase I: paired homologous chromosomes align across equator of cell
Anaphase I: homologous chromosomes separate to opposite poles of the cell
Telophase I: nuclear envelope partially assembles around chromosomes; spindle disappears, cytokinesis divides cell in two
Prophase II: nuclear envelope fragments; spindleforms and fibres attach to both chromosomes
Metaphase II: chromosomes align across equator of cell
Anaphase II: sister chromatids separate to opposite poles of the cell
Telophase II: nuclear envelopes assemble around two daughter nuclei; chromosomes decondense; spindle dissappears
Four identical haploid daughter cells (1n)
How do genetic differences arise
Independent assortment
Chiasmata
haploid cell variations
independent assortment and chiasmata
independent assortment
yeah haploid cell contains one chromosome from each of the homologous pairs
maternal and paternal chromosomes are shuffled into novel combinations
chiasmata
crossing over
homologous maternal and paternal chromosomes exchange genetic information during prophase 1
are chromosomal disorders inherited
most aren’t such as Down syndrome and Turner syndrome
some are caused by changed in the number of chromosomes and not inherited but occur as random events
turner syndrom
genetic condition where instead of individual being 46 XX they are 45 XO
single X chromosome
meiotic disjunction is most often cause of chromosomal loss
can be mosaic where not all cells have lost X chromosome
