biology IB > D3.2 Inheritance > Flashcards

D3.2 Inheritance Flashcards

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1
Q

DNA

A

Double helix made of complementary bases tied together by hydrogen bonds

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2
Q

Chromatin

A

Uncoiled DNA forming nuceleosomes

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3
Q

Chromosomes

A

Highly coiled chromatin forms visible structure during cell division

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4
Q

Chromatid

A

Single strand of DNA formed during replication (DNA)

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5
Q

Gene

A

Section of DNA that codes for specific protein (heritable factor)

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6
Q

Locus

A

Position or location of a gene in DNA

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7
Q

Allele

A

Different form of a gene different versions of a gene

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8
Q

Dominant allele

A

Will slay was be expressed allele that always expresses its phenotype

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9
Q

Recessive allele

A

Allele that its phenotype is only expressed if in homozygous

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10
Q

Genotype

A

Combination of alleles of one specific gene

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11
Q

Phenotype

A

What is expressed physical attributes given by genotypes

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12
Q

Homozygous dominant

A

Having 2 dominant alleles

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13
Q

Homozygous recessive

A

Having 2 recessive allele

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14
Q

Heterozygous

A

Having 1 dominant and 1 recessive allele

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15
Q

Codominance

A

When both dominant alleles are expressed but provide an intermediate phenotype, intermediate between parents

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16
Q

Monohybrid cross

A

When design a crossing of only one gene

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17
Q

Dihybrid cross

A

Design crossing looking at 2 genes at same time

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18
Q

Test cross

A

Done when combine homozygous recessive with an unknown genotype, to see what is the outcome, define if it homozygous or heterozygous or dominant or recessive

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19
Q

Variation

A

Genetic difference observed in a population

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20
Q

Continuous variation

A

Show a normal distribution phenotype changes due to environmental factors

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21
Q

Discontinuous variation

A

Phenotype cannot change throughout life

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22
Q

What are the types of mutations

A

Chromosomal mutation
Genetic mutation

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23
Q

Chromosomal mutation

A

Causes more severe disorders as they are a consequence of non disjunction at anaphase of meiosis (formation of gametes with extra or less chromosomes)

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24
Q

Genetic mutation

A

Caused by deletion misense or nonsense base substitution etc.
causes less severe disorders as involves changes in nitrogenous base sequences

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25
Types of chromosomal mutation
Aneuploidy- 45 chromosomes caused by fusion n-1 Trisomy- 47 chromosomes n+1
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Types of genetic mutation
Sex-linked: involves 23rd pair of chromosome Autosomal- involves chromosomes 1-22
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Types of sex linked mutations
X-linked Y-linked
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Types of autosomal mutations
Dominant- e.g. Huntington Recessive- e.g sickle cell anemia, cystic fibrosis, PKU
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Explain X-linked mutations
E.g haemophilia, colour blindness Both are recessive disorders so there are much higher changes of developing in males
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Haemophilia
Lacks specific clotting factors takes longer to form scabs
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Colour blindness
Lacks one or two cones (photoreceptors)
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Sickle cell anemia
Autosomal recessive Not sex linked Mutation chromosome 11 Type mutation: point mutation, substitution Glu -> Val in codon 6 Affected protein: hemoglobin beta chain Affects oxygen transport in RBC Causes, anemia, fatigue, pain, swelling hand and feet’s, delayed growth
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Cystic fibrosis
Autosomal recessive Not sex linked Chromosome number 7 Deletion mutation Affected protein: CFTR Biological process affected, chloride ion transport across epithelial cells Causes thick mucus, chronic lung infections, digestive issues, poor growth, salty skin
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Hemophilia
Recesssive sex linked X chromosome Mutation: Inversion, deletion and point mutation Effected protein: haemophilia A and B, clotting factors Biological process affected: blood clotting cascade Symptoms: excessive bleeding easy bruising, joint bleeds
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Huntingtons disease
Autosomal dominant Not sex linked Chromosome number 4 Mutation: nucleotide repetition Affected protein: Huntington Biological process affected: neuronal function and survival Symptoms: involuntary movements congestive decline, mood disturbances and personality changes
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Phenyketonuria (PKU)
Autosomal recessive Not sex linked Chronometer number 12 Misense base substitution mutation Affected protein: phenylalanine hydrokylase (PAH gene) Biological process affected: phenylalanine metabolism Symptoms: intellectual disability seizures, musty body odor, behavioral problems, lighter skin and hair
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Red green color blindness
Recessive Sex linked Chromosome x Gene deletion or point mutation Effected Effect protein: o-sins Biological process affected: color vision perception Symptoms: difficulty distinguishing red from green hues
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State genetic term for Sex cell
Gamete
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State the genetic term for Different form of a gene
Allele
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State the genetic term for an allele which only affects the phenotype when two copies of this allele are present
Recessive
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State the genetic term an allele which always affects the phenotype
Dominant
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State the genetic term for having a pair of identical alleles
Homozygous
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State the genetic term for having two different alleles
Heterozygous
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State the genetic term for the appearance of an organism with respect to its gene
Phenotype
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State the genetic terms for the genetic make up of an organism
Genotype
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What are mutations
Are random undirected spontaneous changes in DNA molecules, can be as simple as a change in one base or as significant as a change to an entire autosome
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What does a mutation called non disjunction mean
Occurs during meiosis, can result in an extra chromosome in a gamete Often lethal, but with chromosome number 21 results in Down syndrome
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What does the PAH gene do
Converts amino acids, phenylalanine into amino acid tyrosine Tyrosine- used to make several types of hormones, neurotransmitters and melanin
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What does the mutation to the PAH gene cause
No enzyme to be produced Consequently causes tyrosine deficiency and PAH to accumulate to toxic levels, causes progressive brain damage and retardation There is no cure just treatment with diet and tyrosine supplement
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What are foods which are high with phenylalanine
Fish Milk Meat Dairy Eggs Beans In general high protein foods
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What are foods with low phenylalanine
Most vegetables Fruit Sugars Low protein foods
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What are the antigens present in each of the blood groups
A = A B = B AB = AB O = none
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What are the antibodies present in each of the blood groups
A = anti-B B = anti-A AB = none O = anti-A and anti-B
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What are the genotypes of each blood group
A: IAIA IAi B:IBIB IBi AB: IAIB O: ii
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What are the blood groups each blood group can receive blood from
A: A, O B: B, O AB: A, B, AB, O O: O
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What are the blood groups each blood group can give blood to
A: A, AB B: B, AB AB: AB O: A,B,AB,O
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Sickle cell anemia how do you represent the genes
HB ^ A HB^ A = normal haemoglobin HB ^ A HB ^ S = carrier HB ^ S HB ^ S = affected
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What does codominance mean
When a phenotype produced is different or mix from parents phenotypes
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What is malaria
A parasitic disease caused by plasmodium (kingdom of protist) carried by anopheles mosquito and invades normal RBC (zoonotic) plasmodium invades RBC causes them to lose (burst), plasmodium reproduces inside RBC, bursts releasing more pathogens in blood Common symptoms: fever, shivering, vomiting, anemia, death, kidney failure
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What’s the relationship between plasmodium and sickle cell anemia
Plasmodium finds it harder to infect sickle cell Having only the trait and not the disease, being heterozygous for the disease makes individual resistant (not immune more resistant to infection) to disease, That’s why sickle cell is more prevalent around areas malaria endemic
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Why is having sickle cell anemia an example of natural selection
Having sickle cell trait (heterozygous) means individual has protection against malaria, this gives the individual a selective advantage/ adaptation which makes them more adapted to live in places where malaria is predominant (such as Africa), this makes it an example of natural selection. Meaning the individual can reproduce and pass on mutated allele to future generation, making their offspring also resistant against malaria
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Is sickle cell an example of codominant disease
Yes
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Describe the blood cells of a person which is only a carrier (heterozygous) of sickle cell anemia
Some cells are sickled Which are not affected plasmodium, can still carry a bit of oxygen (needed until body develops own immunity against plasmodium/ malaria) Normal RBC: affected plasmodium
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Sickle cell disease
Inherited disorder of RBC, recessive autosomal caused by point misense mutation in haemoglobin gene
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Describe the mutation that occurs for an individual to have sickle cell disease
Single base substitution mutation Mutation where a glu turns into Val Glu is hydrophilic while Val is hydrophobic amino acid This creates long inflexible fibers of HB molecules cells become stiff and angular causing them to become stuck in small capillaries HB^s = allele for sickle haemoglobin
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Describe effect of sickle cell disease on haemoglobin production
Haemoglobin becomes sickled since mutation causes creation of long inflexible hydrophobic fibers which carries less o2
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Descobre effect of sickle cell disease in terms of symptoms and mortality
Eye damage Fatigue and decreased haemoglobin Swelling and inflamtion of fingers and toes Life expectancy Mitch lower around 45 years
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Describe the difference between sickle cell anemia and sickle cell trait
Anemia: - inherited disorder of HB gene - recessive homozygous - causes carrying of low o2 - Hbs Hbs Trait (carrier) - heterozygous -HbA Hbs - some RBC are normal and some sickled
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Dihybrid cross with unlinked genes
Involves crossing 2 different genes Discovered by Mendel when studying pea colour and shape, and their ratio of offsprings phenotypes when 2 heterozygous parents are crossed,
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Define unlinked genes
Found on different chromosomes Or found very distant apart on the same chromosome
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Do unlinked genes have independent assortment
Yes because of the random orientation of homologous chromosome pairs during meiosis the allele received for one gene doesn’t affect the allele received for the other
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What is the inheritance pattern in unlinked genes
Offspring has equal possibility of inheriting any potential phenotypic combination, in a double heterozygous organism (AaBb) this results in the formation of all 4 possible types of gametes with equal or 25% frequency
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Dihybrid cross outcomes between 2 heterozygous organisms with unlinked genes
Phenotypic ratio- 9:3:3:1
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Dihybrid cross outcomes between one heterozygous and one homozygous recessive organism
Phenotypic ratio 1:1:1:1
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Linked genes definition
Found very close together on the same chromosome
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To linked genes have independent assortment
No because the genes tend to be passed as a unit to gametes more frequently
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Inheritance pattern of linked genes
Offspring with linked genes will only express the phenotypic combinations present in either parent unless crossing over occurs
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Dihybrid cross outcomes between 2 heterozygous organisms with linked genes
Phenotypic ration: 3:1
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Dihybrid cross outcomes between one heterozygous organism and one homozygous recessive organism with linked genes
Phenotypic ratio 1:1:0.1:0.1
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How do you display linked genes vs unlinked genes
Unlinked: AaBb (normal) Linked: A| |a B| |b
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What increases the chance of recombination of genes
When genes are further apart in the chromosome
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How can recombination lead to variation in the genotype of gametes
Alleles are exchanged between non sister chromatids during prophase 1 of meiosis
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What are features that would show that a cell is dividing by meiosis and not mitosis
Recombinant chromatids Presence of homologous chromosomes
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What’s a chi square
Statistical tool that helps us to decide if the observed ratio is close enough to the expected ratio The result is concluded by analyzing the calculated chi squared and the tabulated chi squared at p=0.05
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If calculated chi squared is mallet than tabulated
There is an association, data fits prediction
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If calculated chi square is bigger than tabulated chi squared
There is no association, does not fit prediction
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Equation to calculate chi square
Sum of (O-E) ^2 Divided by E O- observed E- expected
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Monohybrid
Phenotypes determined by one single gene e.g. blood type Follows discontinuous variation (random)
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Phenotypic plasticity
Ability to change the physical appearance of an organism to better adapt to its environment without changing the genotype Most phenotypic plasticity is reversible as when the environment returns to normal the traits readjusts E.g. epidemics: Methylation- addition of CH3 to cytosine Acetylation- addition of acetyl group to histone
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Polygenic
Multiple alleles not genes Phenotypes that are determined by 2 or more genes e.g. skin colour, height Follows continuous variation (highly influenced by environment) follows normal distribution Can cause phenotypic plasticity adapting to conditions for instance, melanin, fur colour etc.
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Incomplete dominance
Neither dominant alleles are fully expressed when present in a heterozygous organism Heterozygous present a blend of mixed phenotypes that is unique
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Complete dominance
Dominant alleles are always expressed (even heterozygous)
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Co dominance
Both dominant alleles are expressed at the same time, producing unique phenotype e.g. blood type AB, calico cats
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Exemple of a sex linked genetic disorder
Haemophilia
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Phenotype definition
Observable traits of an organism
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Incomplete dominance
Heterozygotes have an intermediate phenotype
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Unlinked genes
Segregate in meiosis 1 Undergo independent assortment
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Dihybrid cross with individuals that are heterozygous for both genes will result in which of the following phenotype ratios
9:3:3:1
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Difference between Monohybrid cross and Dihybrid cross
Mono- analyze the inheritance of a single trait Di- explore simultaneous inheritance of 2 independent traits
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Linkage vs crossing over
Linkage- tendency of genes to stay together in a chromosome Crossing over- genetic material gets exchanged between non sister chromatids
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Multiple alleles vs polygenes
Multiple alleles- existance of more than 2 forms of a gene Polygenes- characteristics influenced by more than one gene
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