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IB Bio > Review set 4 > Flashcards

Review set 4 Flashcards

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Biology 101 flashcards
1
Q

what is meiosis

A

Meiosis produces 4, haploid (n = one copy of each chromosome) cells from 1, diploid (2n) cell

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2
Q

What is a Haploid cell?

A

Haploid cells are gametes (sperm/ ova) – come together at fertilization to create a zygote

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3
Q

Meiosis 1 steps

A
  1. Prophase I– Synapsis: homologous chromosomes (similar in shape/ size/ gene arrangement) line up next to each other (bivalents/ tetrads)
    Crossing over: Non-identical sister chromatids exchange DNA – cross over at places called chiasmata, chromosomes break in identical locations, pieces exchanged – creates NEW combinations of genes (recombinations)
  2. Metaphase I— Random orientation: homologous chromosomes line up randomly along middle of cell (2n possible orientations)
  3. Anaphase I– Spindle fibers pull homologous chromosomes to opposite ends of the cell (independent assortment – genes on different chromosomes separate independently of each other)
  4. Telophase I- Reduction division (cytoplasm divides – each new cell now haploid)
    Reduction division (cytoplasm divides – each new cell now haploid)
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4
Q

Prophase I

A

Synapsis: homologous chromosomes (similar in shape/ size/ gene arrangement) line up next to each other (bivalents/ tetrads)
Crossing over: Non-identical sister chromatids exchange DNA – cross over at places called chiasmata, chromosomes break in identical locations, pieces exchanged – creates NEW combinations of genes (recombinations)

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5
Q

Metaphase I

A

Random orientation: homologous chromosomes line up randomly along middle of cell (2n possible orientations)

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6
Q

Anaphase I

A

Spindle fibers pull homologous chromosomes to opposite ends of the cell (independent assortment – genes on different chromosomes separate independently of each other)

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7
Q

Telophase I

A

Reduction division (cytoplasm divides – each new cell now haploid)

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8
Q

Meiosis 2 steps

A
  1. Prophase II–New meiotic spindle forms (eggs in females arrested in this stage)
  2. Metaphase II– Chromosomes (made of sister chromatids) line up along middle of cell
  3. Anaphase II– Centromeres break, sister chromatids separate, one copy of each pulled to opposite ends of cell
  4. Telophase II– Cytoplasm divides: 4 haploid cells that are genetically UNIQUE
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9
Q

Prophase II

A

New meiotic spindle forms (eggs in females arrested in this stage)

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10
Q

Metaphase II

A

Chromosomes (made of sister chromatids) line up along middle of cell

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11
Q

Anaphase II

A

Centromeres break, sister chromatids separate, one copy of each pulled to opposite ends of cell

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12
Q

Telophase II

A

Cytoplasm divides: 4 haploid cells that are genetically UNIQUE

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13
Q

Infinite genetic variation in meiosis explain how?

A

Crossing over in prophase I and random orientation in metaphase I (random fertilization with another individual too – takes into account THEIR crossing over and random orientation!)

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14
Q

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 have an extra chromosome (trisomy – three copies when fertilized)

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15
Q

How is Nondisjunction Diagnosed?

A

Karyograms
Fetal cells obtained from amniotic fluid (amniocentesis) or chorionic villus (placenta) Chromosomes arranged in pairs according to size/ structure 23rd pair used to diagnose gender (XX = female, XY = male)

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16
Q

Define Genetics

A

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

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17
Q

Define Prokaryote

A

circular, naked (no proteins) chromosome – passed directly to offspring (asexual reproduction)

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18
Q

Define Eukaryote

A

linear, with proteins (histones) – many pairs, passed to offspring through sexual reproduction
Pairs #1-22 in humans = autosomes, Pair #23 in humans = sex chromosomes (determine gender)

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19
Q

Genes are carried on

A

Chromosomes– genes are heritable factors (DNA) that determine specific traits (code for proteins)
The complete set of all DNA base sequences of an organism is its genome
#’s of genes/ chromosomes/ genome size UNIQUE to different species (more DNA does NOT always mean an organism is more complex/ advanced than another)

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20
Q

Define Locus

A

Place where a specific gene is located

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21
Q

Define Alleles

A

Genes that show up differently or come in different forms

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22
Q

How are Dominant Alleles written and Recessive alleles written?

A

Dominant Alleles= stronger and Capital Letter

Recessive alleles= weaker and lowercase letter

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23
Q

Define Phenotype

A

The physical expression of a trait (what you SEE)

24
Q

Define Genotype

A

the combination of alleles an organism has for a trait are its genotype

25
Q

Different types of Genotypes

A

heterozygous (different alleles – Aa) or homozygous (same alleles – AA = homozygous dominant, aa = homozygous recessive)

26
Q

What are Heterozygous individuals?

A

Carriers they CARRY recessive alleles but do not show them in their phenotype due to the presence of a dominant allele (im

27
Q

What is codominance? Give an example

A

Equal in strength – both SHOW if present

Blood type

28
Q

How do you write blood type correctly?

A

Type A: I^A
Type B: I^B
Type O: i

29
Q

Genes carried on the sex chromosome are

A

Sex linked

30
Q

X and Y are not

A

HOMOLOGOUS

31
Q

Sex linked traits are more commonly seen in

A

males: Only one X chromosome (whatever inherit will show – no other chromosome to overpower etc.)

32
Q

2 examples of sex linked conditions

A

Hemophilia and red-green color blindness on X-chromosome; Males inherit X from their mothers; IF recessive allele (for hemophilia or color blindness etc.) is on that X, the man WILL have the condition (Xn Y)

33
Q

For sex linked traits what is only possible for females

A

To be the carrier

34
Q

Some genes are Polygenic. What does that mean/entail? And Examples

A

Polygenic traits show CONTINUOUS (bell-shaped curve) variation (not discrete variation)
Phenotypes do NOT fit into distinct categories; phenotypes are continuous because SO many alleles influence the expression of the gene: SKIN COLOR (melanin), HEIGHT, HAIR COLOR etc.

35
Q

How to find if a parent that is showing the dominant trait is Homozygous dominant or Heterozygous?

A

do a TEST CROSS – mate with homozygous recessive – if any of offspring show recessive phenotype, parent is heterozygous, if all offspring show dominant phenotype, parent is homozygous dominant

36
Q

Mutations in Genetic material: What happens and example

A 
Changes in genetic material (DNA): rare
Base substitution (one base in DNA changed; causes wrong codon in mRNA; causes wrong amino acid in translation)
Example: Sickle cell anemia (in DNA: GAG changed to GTG; in mRNA: wrong codon codes for valine instead of glutamic acid, in polypeptide chain): Hemoglobin misshapen (sickle shaped) – cannot carry oxygen as well
37
Q

What changes in Sickle Cell Anemia

A

GAG changed to GTG; in mRNA: wrong codon codes for valine instead of glutamic acid, in polypeptide chain causing the sickle shape

38
Q

WHY does the sickle cell allele (and other disease-causing alleles) persist in populations if so detrimental?

A

Provides SOME advantage (malaria resistance with sickle cell) – only beneficial if you LIVE in an environment where malaria is present though. The ENVIRONMENT determines if the allele is good or bad

39
Q

Do a dihybrid cross right now with TtRR and TTRR.

A

Check it

40
Q

What is a Dihybrid cross?

A

Heterozygous cross shows phenotypic ratio of 9:3:3:1 (TtRr x TtRr) – numbers in ratios are out of 16
To set up punnett square (4x4), NUMBER the alleles in the genotypes (1,2,3,4) and place the following combinations over/ next to each box for each parent (1,3), (1,4), (2,3), (2,4)

41
Q

Dihybrid Cross and linked genes? With an named example

A

Thomas Hunt Morgan and fruit flies
- Linked genes do NOT follow law of independent assortment: inherited together because on SAME chromosome
- Do NOT show typical ratios (9:3:3:1 or 1:2:1 etc) – VARY significantly (Chi-square test, comparing observed and expected, shows significant difference between observed and expected phenotype ratios in offspring)
Genotypes written as VERTICAL pairs with TWO horizontal lines in between them
- ONLY way for recombination in linked genes is crossing over (prophase I): unlinked genes follow independent assortment to create new combinations (of chromosomes)
- MOST offspring will show parental phenotypes because genes inherited TOGETHER on same chromosome (only a small percentage show NEW phenotypes, not present in parents – from crossing over- these are recombinants)
Example: Fly with grey body and long wings (GgLl) crossed with fly with black body and short wings (ggll)
MOST offspring will have grey bodies with long wings (like mom) OR black bodies with short wings (like dad)
IF have grey body with short wings OR black body with long wings, crossing over occurred (these are recombinants = different phenotypes from mom and dad)

42
Q

Name a genetic disease that is caused by a dominant allele?

A

Huntington’s disease

43
Q

Analysis the pedigree on Ms. Mann’s slideshow. Tell if it is sex linked and if it is dominant or recessive

A

Not sex linked and its recessive

44
Q

How to make multiple copies of a gene?

A
  1. PCR (polymerase chain reaction) – makes MANY copies of SMALL amount of DNA (“amplifies” it) using a thermocycler
  2. Gene cloning (clone = genetically identical copy) using recombinant DNA
    Produce recombinant DNA (DNA from two or more different sources/ organisms) Cut vector (plasmid) and gene of interest with restriction enzyme (endonuclease) Combine DNA fragments (will base pair at sticky ends) Add DNA ligase (to seal fragments together) Insert recombinant DNA back into host (bacteria, yeast, sheep etc) Able to do because DNA/ genetic code UNIVERSAL! Allow cells to reproduce gene (and make protein)
    Ex: Insulin for diabetics , Factor IX for hemophiliacs
45
Q

PCR-

A

makes MANY copies of SMALL amount of DNA (“amplifies” it) using a thermocycler

46
Q

Gene cloning (clone = genetically identical copy) using recombinant DNA

A

Produce recombinant DNA (DNA from two or more different sources/ organisms)
Cut vector (plasmid) and gene of interest with restriction enzyme (endonuclease)
Combine DNA fragments (will base pair at sticky ends)
Add DNA ligase (to seal fragments together)
Insert recombinant DNA back into host (bacteria, yeast, sheep etc)
Able to do because DNA/ genetic code UNIVERSAL!
Allow cells to reproduce gene (and make protein)
Ex: Insulin for diabetics , Factor IX for hemophiliacs

47
Q

Gene Transfer

A

Recombinant DNA made (donor + host) and placed into host organism
Host organism now transgenic (GMO = genetically modified organism): has had an artificial genetic change to its genome
Genes transferred to treat disease (gene therapy), for medical treatments (insulin), and for commercial use (crops/ livestock)

48
Q

Pros vs cons of GMO crops

A

Pros:
Added nutrients (vitamin A/ beta carotene in rice)
Higher yields, longer shelf life
Resistance to herbicides, drought, cold etc.; Reduced need for pesticides (harmful to humans etc.)
Cons:
Introduced genes cause allergies (long term effects on human health unknown)
Introduced genes mutate (outcompete wild populations and/ or spread/ cross species) and reduce genetic variation/ biodiversity (Potato blight/ Bt corn)
Monopolies on food production (small farms out of business?)

49
Q

What are the types of cloning?

A

Reproductive cloning, and Therapeutic cloning

50
Q

Reproductive Cloning

A

Take nucleus of differentiated cell and place in egg (remove egg’s nucleus first) – somatic nuclear transfer
“Zap” with electricity (to trick it into thinking it’s fertilized)
Mitotic divisions in “embryo”
Place “embryo” in surrogate mother and allow to develop into baby (CLONE – exact genetic copy)

51
Q

Therapeutic cloning

A

Use embryonic stem cells (undifferentiated) to produce new tissues for transplantation
Arguments for: can be screened for genetic abnormalities; natural process (identical twins); increased chance of offspring (for infertile couples); helps burn victims/ paralysis/ leukemia patients etc.; reduced risk of rejection (genetically identical)
Arguments against: destroys embryo (when does life begin?); higher rates of miscarriage/ developmental disorders; long term health effects unknown; suppression of patient’s immune system risky; human clones?

52
Q

Human Genome project

A

ALL base sequences (including mutations) sequenced for humans (as a species) – Sanger technique with dideoxynucleotides (ddNT’s)/ computers
Mapping outcome: know number, location, and basic sequence of all human genes
Screening outcome: Specific gene probes to detect genetic disorders/ carriers
Medical outcome: Specific genes targeted to produce specific proteins for those who cannot
Ancestry outcome: Improved insight into human origins/ evolution/ migration patterns etc.

53
Q

Gel Electrophoresis

A 
DNA sample (from crime scene, bones, father/ baby) amplified (many copies) using PCR
Cut DNA with restriction enzymes then run through gel using electric current (separates based on SIZE and charge – fragment lengths UNIQUE to each individual due to unique sequences of DNA)
Produces banding pattern in gel (bands represent sizes of fragments – smaller fragments travel faster/ farther)
54
Q

What is gel Electrophoresis used for?

A

Used in DNA Profiling (typically use highly repetitive/ satellite DNA because unique to every individual):

  1. Forensic Investigations (identifies crime scene suspects/ victims)
  2. Paternity testing (half of baby’s bands from mom, other half MUST come from dad)
55
Q

Look at the Gel Electrophoresis slide that shows examples of what it would work?

A

Ok how do you feel about it?

IB Bio (8 decks)

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