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IB Bio > Review #4 presentation > Flashcards

Review #4 presentation Flashcards

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Biology 101 flashcards
1
Q

What are the problems in meiosis

A

Non-disjunction
- failure of sister chromatids to separate (anaphase II)
- cells produced missing a chromosome (monosomy: one copy only when fertilized)
or they have an extra chromosome (trisomy: three copies when fertilized)

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2
Q

how is nondisjunction diagnosed

A

Karyograms

  • fetal cells obtained from amniotic fluid (amniocentesis) or chorionic villus (placenta)
  • chromosomes are arranged in paris according to size and structure
  • 23rd pair used to diagnose gender (XX female XY male)
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3
Q

what is genetics

A

science of heredity (pass on of genetic material from parent to offspring)

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4
Q

prokaryotes genetics

A

circular, naked (no proteins) chromosomes

pass directly to offspring (asexual reproduction)

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5
Q

eukaryotes genetics

A

linear with proteins (histones)
many pairs
passed to offspring through sexual reproduction

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6
Q

genes are carried on …

A

chromosomes

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7
Q

what are genes

A

heritable factors (DNA) that determine specific traits (code for proteins)

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8
Q

what is a genome

A

the complete set of all DNA base sequences of an organism

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9
Q

what is unique to different species

A

number of genes, chromosomes, and size of genome

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10
Q

more DNA does not always mean…

A

that an organism is more complex/advanced than another

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11
Q

What is a genes location on specific places of chromosomes

A

locus

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12
Q

what are the different forms of genes

A

alleles

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13
Q

two things that an allele can be

A

dominant or recessive

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14
Q

what is the difference between dominant and recessive

A

dominant: stronger - written with a capital letter
recessive: weaker - written with lowercase letter

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15
Q

what is the physical expression of a trait (what you see)

A

phenotype (ie Green eyes)

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16
Q

what is a genotype

A

combination of alleles an organism has for a trait (ie: bb)

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17
Q

What can genotypes be

A

heterozygous: different alleles - Aa
homozygous: same alleles
homozygous dominant: AA
homozygous recessive: aa

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18
Q

what is a carrier

A

a heterozygous individual (Nn)
they carry recessive alleles but do not show them in their phenotype due to the presence of a dominant allele
this is important in sex-linked traits and genetic diseases

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19
Q

what are codominant alleles

A

equal in strength alleles - both will show if this is present

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20
Q

what is an example of codominant alleles

A

blood groups

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21
Q

what alleles are equally dominant and what is recessive

A

A (I^A) and B (I^B) are dominant

O (i) is recessive

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22
Q

what are genes carried on

A

sex-chromosomes (sex-linked)

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23
Q

what do males additionally inherit from an egg (mothers)

A

mitochondrial DNA

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24
Q

X and Y are not ______ chromosomes

A

homologous

some genes on larger X chromosome are absent from shorter Y chromosome

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25
Q

What are more commonly seen in males

A

sex-linked traits

only one x chromosome so whatever they inherit will show because there is no other chromosome to overpower it

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26
Q

Examples of sex linked traits

A

hemophilia and red-green color blindness

  • on the x chromosome
  • males inherit x from mother
  • IF the recessive allele is on the X, the man WILL have the condition (XY)
27
Q

Who is a carrier of sex-linked traits

A

females - two X chromosomes so they can be heterozygous -> dominant allele on one X and a recessive allele on the other

28
Q

polygenic

A

genes that have multiple alleles

29
Q

what do polygenic traits show

A

continuous (bell-shaped curve) varition

non-discrete variation

30
Q

Do phenotypes fit into distinct categories

A

no
phenotypes are continuous because so many alleles influence the expression of the gene
(ie: SKIN COLOR (melanin), height, hair color, etc)

31
Q

What is something that could influence the expression of skin color, height, hair color, etc

A

environment: UV liet, diet/nutrition

32
Q

if a dominant phenotype is showing:

A

conduct a TEST CROSS
mate with homozygous recessive
if any offspring show the recessive phenotype - parent is heterozygous
if all offspring show dominant phenotype - parent is homozygous dominant

33
Q

what is a mutation

A

changes in genetic material (DNA)

rare

34
Q

what is base substitution

A

one base in DNA is changed

  • causes wrong codon in mRNA
  • causes wrong amino acid in translation
35
Q

what is an example of a mutation

A

sickle cell anemia
- DNA: GAG is changed to GTG
- mRNA: wrong codon codes for valine instead of glutamic acid in the polypeptide chain
results in the hemoglobin being misshapen (sickle shaped) and can’t carry oxygen as well

36
Q

why does sickle cell anemia and other disease causing alleles persist in populations

A

they can provide some advantages

  • resist to maleria if you have sick cell anemia
    • beneficial if you live an environment where maleria is present
37
Q

what determines if an allele is good or bad

A

ENVIRONMENT

38
Q

dihybrid

A

two trait cross in unlinked genes

39
Q

dihybrid heterozygous cross shows what ratio

A

9:3:3:1

numbers in ratios are out of 16

40
Q

how do you set up a dihybrid heterozygous punnet square

A

4x4
number alleles 1,2,3,4
foil them and place the combinations over the boxes for each parent
1,3 1,4 2,3 2,4

41
Q

dihybrid crosses are ____ genes

A

linked

42
Q

who discovered that dihybrid crosses are linked genes

A

Thomas Hunt Morgan using fruit flies

43
Q

What law do linked genes not follow

A

the law of independent assortment:

they are inherited together because they are on the same chromosome

44
Q

Linked genes do not…

A

show typical ratios (9:3:3:1 or 1:2:1)
vaary significantly
chi-squared test performed: compare observed and expected
this shows the significant difference btw observed and expected phenotype ratios in offspring

45
Q

how are genotypes written for dihybrid crosses

A

vertical pairs with two horizontal lines between them

46
Q

what is the only way for recombination in linked genes

A 
crossing over (phrophase I) 
unlinked genes follow independent assortment to create new combinations of chromosomes
47
Q

why will most offspring show parental phenotypes

A

because genes are inherited together on the same chromosome (only a small percentage of recombinants)

48
Q

what are recombinants

A

New phenotypes, not present in parents from crossing over

49
Q

what are some genetic disorders caused by

A

dominant alleles

ie: huntington’s disease

50
Q

how do you make multiple copies of a gene

A

PCR (polymerase chain reaction)

Gene cloning

51
Q

what is PCR

A

makes many copies of a small amount of DNA (amplifies it) using a thermocycler

52
Q

what is gene cloning

A

clone = genetically identical copy
uses recombinant DNA

  • produce recombinant DNA (DNA from two or more different sources/organisms)
    - cut vector (plasmid) and gene of interest with a restriction enzyme (endonuclease)
    - combine DNA fragments (will base pair at sticky ends)
    - add DNA ligase to seal fragments back together
  • insert recombinant DNA back into host (bacteria, yeast, sheep, etc)
    - able to do this because the DNA code is universal
  • allow cells to reproduce gene and make proteins
    - insulin for diabetics
    - facter IX for hemophiliacs
53
Q

Gene transfer

A
  • recombinant DNA made (donor + host) and placed into host organism
  • host organism is now transgenic (GMO) has had an artificial change to its genome
  • genes transferred to treat disease (gene therapy) for medical treatments (insulin), and commercial use (crops)
54
Q

pros to GMO crops

A
  • added nutrients (vitamin A in rice)
  • higher yields
  • longer shelf life
  • resistance to herbicides, drought, cold, etc
    • reduced need for pesticides
55
Q

cons of gmo crops

A
  • introduced genes cause allergies
  • long term effects on human health unknown
  • introduced genes mutate (outcompete wild populations and or cross species)
  • reduce genetic variation (potato blight)
  • monopolies on food production
56
Q

what is reproductive cloning

A

exact genetic copy of entire organism using adult, differentiated cells

  • remove an egg’s nucleus
  • take nucleus of differentiated cell and place in egg (somatic nuclear transfer)
  • zap with electricity to trick it into thinking it’s fertilized
  • mitotic divisions in embryo
  • place embryo in surrogate mother and all to develop into baby
57
Q

what is theraputic cloning

A
  • use embryonic stem cells (undifferentiated) to produce new tissues for transplantation
58
Q

arguments that support theraputic cloning

A
  • can be screen for genetic abnormalities
  • natural process (identical twins)
  • increased change of offspring for infertile couples
  • help burn victims, paralysis, and leukemia patients
  • reduce risk of rejection because they genetically identical
59
Q

arguments that are against therapuetic cloning

A
  • destroys embryo (when does life begin)
  • higher rates of miscarriage and developmental disorders
  • long term health effects are unknown
  • suppression of patient’s immune system is risky
  • human clones?
60
Q

human genome project

A

All base sequences including mutations are sequenced for humans as a species

  • mapping outcome: number and location and base sequence for all human genes
  • medical outcome: specific genes targeted to produce specific proteins for those who can’t
  • ancestry outcome: improved insight into human origins/evolution
  • screening outcome: specific gene probes to detect genetic disorders and carriers
61
Q

gel electrophoresis

A
  • DNA sample amplified using PCR (from crime scene, father/baby, bones)
  • Cut DNA with restriction enzymes then run through gel using electric current
    - separate based on size and charge: fragment lengths are unique to each individual due to unique sequences of DNA
  • produces banding pattern in gel
    • band represent sizes of fragments, smaller fragments travel faster)
62
Q

what is gel electrophoresis used in

A

DNA profiling (typically use highly repetive DNA because it is unique to every individual

  • Forensic investigations (identify victims and suspects
  • paternity testing (half of babys bands from mom and half from dad)
63
Q

DNA profiling and gel electrophoresis

A
  1. amplify DNA samples using PCR then cut with restriction enzymes (endonucleases)
  2. run samples through gel electrophoresis and analyze banding patterns (show fragments lengths and sizes)
    • can also add probes (fluorescently labeled specific, complementary DNA sequences) to gels to identify genes of interest and can cause disease (sickle cell)

IB Bio (26 decks)

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