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HAN 202 > Chapter 29 Hereditary > Flashcards

Chapter 29 Hereditary Flashcards

1
Q

genetics

A
  • study of the mechanism of hereditary
  • basic principles of genetics were proposed in mid-1800s by Mendel, who studied inherited characteristics that were either all or none
  • human traits are much more complex than that
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2
Q

Human Genome Project (1990-2003)

A
  • has determined human DNA sequence, which can aid in genetic research and genetic screening
  • cost 3 billion dollar
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3
Q

genetics introduction

A
  • development of a new individual is guided by the gene-bearing chromosomes it receives from its parents
  • diploid number of chromosomes:
  • diploid number = 46 (23 pairs of homologous chromosomes) = 2n
  • in all cells except gametes (egg or sperm)
  • haploid number = 1n
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4
Q

chromosomes

A
  • homologous chromosomes are pairs of chromosomes -> one set from egg and one from sperm
  • 1 pair of sex chromosomes determines the genetic sex ( XX - female, XY - male)
  • 22 pairs of autosomes guide expression of most other traits
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5
Q

gene pairs (alleles)

A

-alleles are genes that occur at same locus (location) on homologous chromosomes

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6
Q

homozygous

A

alleles controlling a single trait are the same

  • TT
  • tt
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7
Q

heterozygous

A
  • alleles for a trait are different

- Tt

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8
Q

dominant

A

-an allele that masks or suppresses its (recessive) partner

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9
Q

Gregor Mendel

A
  • austrian monk
  • 1822
  • teacher, in charge of monastery garden
  • two types of pea plants- tall and short
  • self pollinating vs cross pollination
  • cross pollinating a tall and short plant produces all tall plants, but next generation will produce 3 tall and 1 short (25%)
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10
Q

karyotype

A

-diploid chromosomal complement displayed in homologous pairs

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11
Q

genotype

A

-the genetic makeup (Tt)

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12
Q

phenotype

A

-the way the genotype is expressed (tall pea plant)

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13
Q

sexual sources of genetic variation

A
    1. chromosomes segregation and independent assortment
    1. crossover of homologous
    1. random fertilization of eggs by sperm
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14
Q

segregation and independent assortment

A
  • independent assortment- during gametogenesis, maternal and paternal chromosomes are randomly distributed to daughter cells, occurs during metaphase of meiosis
  • segregation- distribution of 2 alleles for a trait to different gametes during meiosis
  • the number of gamete types = 2^n, where n is the number of homologous pairs
  • ex. in a mans testes, 2^n = 2^23 = 8.5 million
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15
Q

crossover and genetic recombination

A
  • genes on the same chromosome are linked
  • chromosomes can cross over; forming a chiasma, and exchange segments
  • crossover occurs during prophase of meiosis
  • recombinant chromosomes have mixed contribution from each parent
  • homologous chromosomes synapse during prophase of meiosis 1
  • each chromosome consists of two sister chromatids
  • one chromatid segment exchanges positions with a homologous chromatid segment- AKA- crossing over occurs forming a chiasma
  • the chromatids forming the chiasma break, and the broken off ends join their corresponding homologues
  • at conclusion of meiosis, each haploid gamete has one of the 4 chromosomes -> two of the chromosomes are recombinant (they carry new combinations of genes)
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16
Q

random fertilization

A
  • random fertilization adds to a genetic variation because any sperm can fuse with any ovum (unfertilized egg)
  • 70 trillion diploid combinations- not counting crossing over!
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17
Q

types of inheritance

A
  • most traits are determined by multiple alleles or by the interaction of several gene pairs:
  • dominant-recessive inheritance
  • multiple allele inheritance
  • polygene inheritance
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18
Q

dominant-recessive inheritance: punnett square

A
  • reflects the interaction of dominant and recessive alleles
  • punnett square- predicts the possible gene combinations resulting from the mating of parents of known genotypes
  • ex. probability of genotypes from mating two heterozygous parents (Tt)
  • T- tongue roller and t- cannot roll tongue
  • TT and tt are homozygous; Tt is heterozygous
  • creates- TT, tt, Tt, Tt
19
Q

simple dominant recessive inheritance

A
  • A) attach earlobes (unattached-dominant)
  • B) roll tongue
  • C) dimples
  • D) freckles
  • E) curly hair
  • F) cleft chin
  • G) widows peak
  • H) hand crossing (left on top is dominant)
20
Q

dominant disorders

A
  • uncommon because many are lethal and result in death before reproductive age
  • EXCEPTION- huntingtons disease- caused by a delayed action gene- person survives long enough to reproduce
21
Q

dominant-recessive inheritance

A
  • most genetic disorders are inherited as simple recessive traits
  • albinism, cystic fibrosis, and Tay-Sachs disease
  • heterozygotes are carries who do not express the trait but can pass it on to their offspring
22
Q

The ______ is an individuals outward appearance while the ______ is an individual genetic makeup

A
  • phenotype; genotype*
  • genotype; phenotype
  • allele; gene
  • gene; allele
23
Q

a person whose genetic makeup includes the gene pair bb is _____

A
  • codominant
  • heterozygous
  • homozygous dominant
  • homozygous recessive*
24
Q

incomplete dominance

A
  • heterozygous individuals have an intermediate phenotype
  • ex. sickling gene
  • SS= normal Hb is made
  • Ss= sickle cell trait (both aberrant and normal Hb are made); can suffer a sickle cell crisis under prolonged reduction in blood O2
  • ss= sickle cell anemia (only aberrant Hb is made; more susceptible to sick-cell crisis
25
Q

multiple allele inheritance

A
  • genes that exhibit more than two allele forms
  • ABO blood grouping is an example
  • three alleles (I^A, I^B, i) determine the ABO blood type in humans
  • I^A and I^B are codominant (both are expressed if present), and i is recessive
26
Q

sex-linked inheritance

A
  • inherited traits determined by genes on the sex chromosomes
  • X chromosomes bear over 1400 genes (many for brain function); Y chromosomes carry about 200 genes
  • more than 100 sex-linked disorders have been mapped to the X chromosomes
  • X-linked genes are found only on the X chromosome, and are typically passed from mothers (carriers) to sons (e.g. hemophilia or red-green color blindness)
  • daughters remain unaffected or carrier
  • this is because daughter take both XX and the dominant will remain dominant…if the son inherits only the carrier X it will present itself
  • males have just one X chromosome, thus all X-linked alleles are expressed in males, even if recessive
27
Q

why are most calico cats female

A
  • coat color is determined by X chromosome
  • one X has allele for black spots
  • one X has allele for orange spots
  • female cats can have a combination of black and orange spots, males (only one X) can have only one color
28
Q

polygene inheritance

A
  • depends on several different gene pairs at different locations acting in tandem
  • results in continuous phenotypic variation between two extremes
  • ex. skin color, eye color, height, metabolic rate, intelligence
  • skin color is controlled by 3 separately inherited genes, each existing in 2 allelic forms: A, a; B, b; C, c
  • the A, B and C alleles confer dark skin pigment and their effects are additive
  • when heterozygous individuals mate, a broad range of pigments is possible
29
Q

chromosomal disorders

A
  • if two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with 3 copies of a chromosome
  • down syndrome- 3 copies of chromosomes 21
30
Q

genotype vs phenotype

A

-genotype (excluding mutations) is unchanging (rock) while phenotype can be molded or changed (clay)

31
Q

phenocopies

A
  • environmentally produced phenotypes that mimic conditions caused by genetic mutation during embryonic development
  • thalidomide babies- medications affected the babies in utero
32
Q

environmental factors

A
  • can influence genetic expression after birth
  • poor nutrition can affect brain growth, body development, and height
  • childhood hormonal deficits can lead to abnormal skeletal growth and proportions
  • getting a tan
33
Q

what is an example of a disease caused by a lethal dominant gene

A
  • tay-sachs disease
  • huntingtons disease*
  • cystic fibrosis
  • sickle cell anemia
34
Q

what is the probability of a mother who has a genotype I^A I^B and a father who has a blood type O having a child who has blood type O

A
  • 0%*
  • 25%
  • 50%
  • 100%
35
Q

beyond DNA: regulation of gene expression

A
  • 3 levels of controls are found in human genome
  • first layer- protein coding genes -> involve less than 2% of a cells DNA
  • DNA that is a blueprint for protein synthesis
  • secondar layer- small RNA -> found in non-protein-coding DNA
  • third layer- epigenetic marks -> stored in proteins and chemical groups that bind to DNA and in a way chromatin packaged
36
Q

small RNAs

A
  • microRNAs (miRNAs) and short interfering RNAs (siRNAs)
  • act directly on DNA, other RNAs, or proteins
  • may silence genes or prevent their expression and appear to play a role in directing apoptosis during development
  • in future, RNA interfering drugs may treat disease such as age-related macular degeneration and parkinsons disease
37
Q

epigenetic marks

A
  • information stored in the proteins and chemical groups bound to DNA
  • determine whether DNA is available for transcription or silenced
  • if DNA is like the alphabet than epigenetic marks are like punctuation
  • epigenetics= study of heritable changes in gene expression -> change in phenotype without change in genotype
  • lifestyle can affect individual epigenetics: pollution and diet
38
Q

extranuclear (mitochondrial) inheritance

A
  • not all DNA Is located in cells nucleus
  • mitochondrial contain 37 of their own genes, referred to as mitochondrial DNA (mtDNA)
  • mitochondria are transmitted to embryo by mother in cytoplasm of egg
  • errors in mtDNA are linked to rare disorders
  • usually problems associated with oxidative phosphorylation (cellular respiration)
  • some muscle and neurological problems, possibly Alzheimer’s and parkinsons disease
39
Q

genetic screening, counseling, and therapy

A
  • newborn infants are routinely screened for a number of genetic disorders: congenital hip dysplasia, imperforate anus, and other metabolic disorders
  • other examples:
  • screening adult children of parents with huntingtons disease
  • testing a women pregnant for the first time after age 35 to see if the baby has trisomy-21 (down syndrome)
40
Q

carrier recognition

A
  • two major avenues for identifying carriers of gene: pedigrees and blood tests
  • pedigrees trace a particular genetic trait through several generation; helps to predict the future
  • blood test and DNA probes can detect the presence of unexpressed recessive genes
  • tay-sachs and cystic fibrosis genes can be identified by such tests
41
Q

fetal testing

A
  • used when there is known risk for a genetic disorder
  • amniocentesis- amniotic fluid is withdrawn after the 14th week and fluid and cells are examined for genetic abnormalities
  • chorionic villus sampling (CVS): chorionic villi are sampled and karyotyped for genetic abnormalities
42
Q

human gene therapy

A
  • genetic engineering has the potential to replace a defective gene
  • defective cells can be infected with a genetically engineered virus containing a functional gene (because they can enter the nucleus)
  • the patients cells can be directly injected with “corrected” DNA
43
Q

ethical issues in human genetics

A
  • if human cells can be manipulated to cure diseases, they can also be manipulated to produce certain traits:
  • height, eye color, sex, appearance, intelligance
  • should we gain the opportunity to design our bodes? human cloning?
44
Q

a color blind man marries a women with normal vision. the womans father was also color blind. what is the chance that their first child will be a color blind son

A
  • 0%
  • 25%*
  • 50%
  • 100%

HAN 202 (16 decks)

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