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Flashcards in Exam 2 Deck (103):
1

DNA

Located in the nucleus of eukaryotes
In loose strands the majority of the time
Condenses into chromosomes prior to division

2

Centromere

Where sister chromatids (pairs) are attached and microtubules bind

3

How many PAIRS of chromosomes are in your nucleus?

23 PAIRS
22 autosomal (homologous)
1 sex pair

4

Mitosis

Exact copies of original cell
Everywhere but sex cells
Growth and repair of our bodies

5

Interphase

Most time spent here
Loose DNA strands
DNA replicates (2 copies of each strand in nucleus)

6

Mitosis

Prophase
Metaphase
Anaphase
Telophase

7

Prophase

DNA condenses into chromosomes
Microtubules form anchored by centrioles
Nuclear envelope begins to break down

8

Metaphase

Chromosomes align at the middle

9

Anaphase

Pulling apart of the sister chromatid to opposite sides of the cell
(Both new cells will have same DNA)

10

Telophase

Nuclear envelope reforms
Chromosomes unravel

11

Cytokinesis

Splitting of one cell into two

12

Pronto-oncogenes

Mitosis regulated by this
If they mutate, they no longer function properly, resulting in cancer

13

Causes of cancer

Inherited mutations
(BRCA 1/BRCA 2=breast cancer)
Environmental carcinogens
(Smoking, UV radiation, HPV virus)

14

Malignant

Tumor invades surrounding tissue
Cancerous

15

Metastatic

Individual cells break off and start a new tumor elsewhere
Cancerous

16

Benign

Tumor has no effect on surrounding tissue
Non cancerous

17

Treating cancer

Surgery
Chemotherapy
Radiation
(Vaccines being developed)

18

Meiosis

Cell division in sex cells
4 cells
Not identical to original
Half the DNA of the original

19

Interphase (same as mitosis)

Copies of DNA
2 in each cell

20

Prophase 1

Chromosomes and chromatid joins at centromere
**crossing over happens here-some chromatids (single strands) with have DNA from both mom and dad

21

Metaphase 1

Homologous chromosomes pair up and randomly align in the middle of the cell

22

Anaphase 1

Homologous chromosomes pulled towards the ends of the cell
**pairs here NOT just strands of DNA

23

Telophase 1/Cytokinesis

Nuclear envelope reforms
Chromosomes unravel into loose strands
Cell splits

24

Prophase 2

DNA condenses
**No crossing over this time

25

Metaphase 2

Chromosomes align in the middle of the cell

26

Anaphase 2

Sister chromatids are pulled pulled apart, splitting the pair

27

Telophase 2/Cytokinesis

Nuclear envelope reforms
Cell splits
**Haploid cells-only contain one copy of a chromosome (original cell was diploid with two copies)
Called gametes

28

Heterozygous

Two different alleles of a gene

29

Homozygous

Same allele of a gene

30

Dominant

One expressed in a heterozygote

31

Recessive

Not expressed in a heterozygote
**expressed in a homozygote

32

Codominance

Both alleles expresses equally but separately

33

Incomplete dominance

Both alleles expressed but the phenotype is intermediate

34

Genotype

Genetic composition of an individual (ex. Bb)

35

Phenotype

The traits expressed by an individual (ex. Brown eyes)

36

Phenotypic plasticity

Same genotype, different phenotype

37

Phenotype is determined by:

Genotype AND environment

38

Mendel (1865)

Work with pea plants is the foundation for genetic inheritance

39

Mendel’s laws of inheritance

1. Segregation-alleles separate from each other during meiosis
2. Independent assortment-alleles of different genes are inherited independently of each other
3. Dominance-some alleles of a gene may be dominant over others

40

Dihybrid cross (both parent heterozygous at two genes)

(RrYy x RrYy)
Phenotypic ratio=9:3:3:1
**only possible is there is independent assortment of alleles from different genes

41

Genes on the same chromosome are often linked

Genes on DIFFERENT chromosomes aren’t linked

42

DNA replication

Occurs in interphase and inside the nucleus

43

DNA replication

Step 1: DNA double helix is unwound by he enzyme Helicase
Step 2: DNA polymerase adds nucleotides complimentary to the original strand

44

DNA replication is semiconservative:

Resulting DNA double helices contain one original strand and one new strand

45

Mutations

DNA polymerase proofreader DNA strands during replication and fixes errors
Errors that don’t get fixed are mutations, that may result in new alleles of a gene

46

Sex chromosomes: what do they contain?

X & Y:
Genes for basic cellular function
Sex determination genes (SRY gene triggers male development)
X: ~800 protein coding genes
Y: ~70 protein coding genes

47

Recessive, disease causing alleles on the X chromosome are more harmful in males

XX-healthy
Xx-healthy carrier
xx-hemophilia

XY-healthy
xy-hemophilia

48

Only 1 X chromosome is “activated” per cell in females

Barr body is the inactivated X chromosome

49

Sex chromosomes cross over in the PAR regions: the ends

Both X to X and X to Y

50

Biological sex

Phenotype base in the combination of chromosomes, hormones, and sex organs

51

Gender

Personal and cultural identity pertaining to biological sex and other factors

52

Transgender

A person whose gender differs from the biological sex they were assigned at birth

53

Why might a person not identify with their assigned sex at birth?

CAH: inability to produce cortisol in XX, leading to masculinization
AIS: inability to produce or possess receptors for androgen in XY, leading to female phenotype
Klinefelter syndrome: individuals are XXY: May exhibit both male and female phenotypes
SRY gene crosses over onto the X chromosome
XXY, male sexual organs develop, male and female hormones

54

Sex determined by egg incubation temp in turtles and reptiles

Turtles
Male: low temp
Female: high temp

Crocodile
Male: high and low temp
Female: mid temp

55

Sequential hermaphroditism

Being able to change sex during the lifetime (clownfish)

56

Platypuses have 10 sex chromosomes

Males: XYXYXYXYXY
Females: XXXXXXXXXX

Similar to platypus autosome 6

57

Birds and butterflies have a ZW sex chromosome system

ZZ-male
ZW-female

58

Honey bees

Diploid: females
Haploid: males (essentially unfertilized gametes)

59

Plants

Most are hermaphrodites: both parts on same plant
Some are dioecious: parts on separate individuals (poison ivy and papaya)

60

Tetrahymena

Have seven different sexes

61

Why did separate sexes and sex chromosomes evoke?

Separate sexes prevents self fertilization and increases genetic diversity

62

How did sex chromosomes evolve?

Autosomes—->sex chromosomes

63

Transcription

Production of mRNA (AUGC)

64

Translation

Step 1: tRNA binds to specific amino acids depending on their RNA sequence
Step 2: rRNA moves across mRNA. tRNA antitoxins bind to mRNA codons, amino acids bind together
Step 3: ribosome reaches a stop codon on the mRNA, translation is finished

65

The genetic code is redundant (several codons code for one amino acid)

But it isn’t ambiguous (any particular codon codes for one specific amino acid)

66

GMO:

Organisms whose genome have been engineered, often incorporating genes from another organism

67

~80% of all processed foods contain at last one GMO

Corn, soybeans, cotton, potatoes, papayas, apples

68

Roundup ready soybeans:

Contain gene from bacteria, which confers resistance to the herbicide Roundup

69

Bt corn

Contains gene from bacteria, which produces toxin against the corn borer insect

70

Upsides of GMO crops

Produce more food

71

Potential downsides

$$
Farmers can only use gmo’d seeds for one harvest

72

GMO medicines

GMO insulin-produced by yeast or bacteria, first GMO medicine
GMO blood clotting proteins (made by goats)

73

Gene therapy (GMO humans) vs CRISPR

Insertion of gene into harmless virus
CRISPR much more specific than virus method

74

Stem cells

Undifferentiated cells that have not yet acquired a specific function

75

Brain stem

Governs reflexes and spontaneous functions
-midbrain: adjusts sensitivity of the eyes and ears
-pons/medulla oblongata: relay messages between spinal cord and brain

76

Cerebellum

Balance, coordination, muscle memory

77

Thalamus

Relay center for sensory signals except smell
Amplifies or suppresses signals before they go to cerebrum

78

Limbic system

Hypothalamus
Amygdala
Hippocampus

79

Hypothalamus

Control center for temperature regulation, blood pressure, thirst, sex drive, emotion
Hormone production
Pituitary gland

80

Amygdala

Fear, pleasure, emotional response
Flight/flight

81

Hippocampus

Learning
Short term memory

82

Cerebrum

Planning, creativity, consciousness, voluntary movement, language

83

Four lobes

Frontal-higher thinking
Parietal-touch
Occipital-visual information
Temporal-auditory information

84

Brain hemispheres

Control the opposite sides of the body

85

Corpus callosum

Connects the hemispheres

86

Cerebrospinal fluid

Cushions and protects the bran from the skull

87

Concussions

Cause shock, headache, confusion
Can cause irritability, trouble sleeping, depression, brain damage

88

Woodpecker traits that reduce concussions

Less cerebrospinal fluid
Spongy bone layer and hard, elastic bone layer (to absorb impact)
Can get brain damage

89

Brain compared to other species
Common wormlike ancestor ~600 million years ago

Human brain-cerebrum wrinkled (increases surface area)
Mouse brain-cerebrum smooth
Dolphin brain-memory, play/experiment, cooperation/problem solving
Bird brain-small, smooth (although highly intelligent), problem solving, memory
Octopus brain-majority of neurons in arms, not the brain, short and long term memory, recognize individuals, no common brain anatomy, independent evolution of a complex brain

90

Central nervous system

Brain and spinal cord

91

Peripheral nervous system

Nerves radiating through the rest of the body

92

Neurons

Specialized cells that carry messages in the brain and nervous system

93

Sensory neurons

Carry information from the body to the CNS

94

Motor neurons

Carry information AWAY from the CNS towards the rest of the body

95

Anatomy of a neuron

Dendrites
Cell body
Axon
Terminal boutons
(Nerves are bundles of axons)

96

How do signals move through a neuron?

Begins at dendrites travels through cell body and axon to terminal bouton
Action potential travels down the axon
Normal charge restored behind action potential

97

How does a nerve impulse travel from one neuron to the next?

Synapse: a junction between two neurons

98

Neurotransmitters

Transmit the signal between neurons at the synapse

99

Removal of neurotransmitters from synapse

Reuptake into pre-synaptic neuron through channel OR digestion by enzymes in the synapse

100

Rene Descartes

Mathematician
Proponent of rational thinking regarding the natural world
Believed that the pineal gland contains the human soul

101

Phrenology

Pseudoscience claiming the shape and size of the skull indicates a person’s personality and abilities

102

Phrenology and the Rwandan genocide

Belgian colonizers (1930s) claimed Tutsis were more “European” than Hutus, and therefore superior
In 94 between 500,000 and a million people were killed within 100 days

103

Sea slugs and the human mind

Sea slugs have large neurons
Molecular basis of learning and memory
Short term memory involves changes in existing synapses, while long term memory builds new synaptic connections