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HAN 202 > Chapter 29: Heredity > Flashcards

Chapter 29: Heredity Flashcards

1
Q

Genetics

A

study of the mechanism of hereditary

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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

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3
Q

Diploid number of chromosomes

A

Diploid number= 46 (23 pairs of homologous chromosomes)= 2n

  • In all cells except gametes -
  • > Haploid number= 1n
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4
Q

1 pair of sex chromosomes determines the genetic sex

A 
XX= female
XY= male
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5
Q

22 pairs of autosomes guide the expression of most other traits

A

TRUE

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6
Q

gene pairs (alleles)

A
  • alleles are genes that occur at same LOCUS (location) on homologous chromosomes
  • homozygous: alleles controlling a single trait are the same (TT, tt)
  • heterozygous: alleles for a trait are different (Tt)
  • dominant: an allele that masks or suppresses its (recessive) partner
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7
Q

Genetics- gregor mendel

A
  • Austrian monk (1822)
  • Teacher, in charge of monastery garden
  • Two types of pea plants – tall and short
  • Self pollinating vs cross pollinating

*cross pollinating a tall and short plant produces all tall plants, but next generation will produce 3 tall and 1 short

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8
Q

genotype

A

the genetic makeup (Tt)

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9
Q

phenotype

A

the way the genotype is expressed (tall pea plant)

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10
Q

sexual sources of genetic variation

A
  1. chromosome segregation and independent assortment
  2. crossover of homologous
  3. random fertilization of eggs by sperm
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11
Q
  1. segregation and independent assortment
A
  • > Independent assortment: during gametogenesis, maternal and paternal chromosomes are randomly distributed to daughter cells, (which allele a gamete recieves for gene A has no bearing on the allele it recieves for gene B)
  • occurs during metaphase of meiosis

-> segregation: distribution of 2 alleles for a trait to different gametes during meiosis

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12
Q

independent assortment

A

during gametogenesis, maternal and paternal chromosomes are randomly distributed to daughter cells,
*occurs during metaphase of meiosis

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13
Q

segregation

A

distribution of 2 alleles for a trait to different gametes during meiosis

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14
Q

segregation and independent assortment

A

-the number of gamete types= 2^n, where n is the number of homologous pairs

ex: 2^3= 8 (2x2x2)
in a man testes, 2^n= 2^23= 8.5 million

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15
Q
  1. 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 contributions from each parent
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16
Q

karyotype

A

diploid chromosomal complement displayed in homologous pairs

17
Q

homologous chromosomes synapse during prophase of meiosis 1. Each chromosome consists of 2 sister chromatids

A

true

review slides 14-17

18
Q

random fertilization

A

adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg)

19
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
20
Q

dominant recessive inheritance

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

traits:

  • attached earlobes (unattached= dominant)
  • roll tongue
  • dimples
  • freckles
  • curly hair
  • cleft chin
  • widows peak
21
Q

dominant disorders

A

are uncommon because many are lethal and result in death before reproductive age

**exception: Huntington’s Disease is caused by a delayed action gene- person survives long enough to reproduce

22
Q

dominant recessive inheritance

A
  • most genetic disorders are inherited as simple recessive traits…. albinism, cystic fibrosis, and tay-sachs disease
  • heterozygotes are carriers who do not express the trait but can pass it on to their offspring
23
Q

incomplete dominance

A

-heterozygous individuals have an intermediate phenotype

  • example: sickling gene
  • SS= normal Hb is made
  • Ss= sickle cell trait (both aberrent 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 sickle cell crisis)
24
Q

multiple allele inheritance

A
  • genes that exhibit more than 2 allele forms
  • ABO blood grouping is an example
  • 3 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

25
sex-linked inheritance
- 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 chromosome
26
sex linked inheritance
X-linked genes are * found only on the X chromosome * typically passed from mothers to sons (e.g hemophilia or red-green color blindness) ***males have just 1 X chromosome, thus all X-linked alleles are expressed in males, even if recessive
27
why are most calico cats female?
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
polygene inheritance
- depends on several different gene pairs at different locations acting in tandem - results in continuous phenotypic variation between 2 extremes - ex: skin color, eye color, height, metabolic rate, and intelligence - Skin color is controlled by 3 separately inherited genes, each existing in 2 allelic forms: A, a; B, b: C, c
29
chromosomal disorders
- if 2 copies of an autosomal chromosome fail to separate during meiosis, and individual may be born with 3 copies of a chromosome - down syndrome: 3 copies of chromosome 21
30
phenocopies
- > genotype: (excluding mutations) is unchanging - > phenotype: can be molded or changed (clay) - > phenocopies: environmentally produced phenotypes that mimic conditions caused by genetic mutations during embryonic development.... thalidomide babies - > environmental factors 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
31
Beyond DNA: regulation of gene expression
3 levels of control are found in human genome - > first layer: protein coding genes * involves less than 2% of a cells DNA * DNA that is blueprint for protein synthesis - > second layer: small RNAs * found in non-protein-coding DNA - > third layer: epigenetic marks * stored in proteins and chemical groups that bind to DNA and in way chromatin packaged
32
small RNAs
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 diseases such as age-related macular degeneration and Parkinson's disease
33
Epigenetic marks
- info 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 then 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 * diet
34
extranuclear (mitochondrial) inheritance
- not all DNA is located in cell's nucleus - mitochondria 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 alzheimers and parkinsons
35
genetic screening, counseling, and therapy
-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 huntington's disease * testing a woman pregnant for the first time after age 35 to see if the baby has trisomy-21 (down syndrome)
36
carrier recognition
- Two major avenues for identifying carriers of genes: pedigrees and blood tests - Pedigrees trace a particular genetic trait through several generations; helps to predict the future - Blood tests and DNA probes can detect the presence of unexpressed recessive genes - Tay-Sachs and Cystic Fibrosis genes can be identified by such tests
37
fetal testing
- Used when there is a known risk of 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
38
human gene therapy
- 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 patient’s cells can be directly injected with “corrected” DNA

HAN 202 (13 decks)

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