Exam 2 Flashcards
DNA
Located in the nucleus of eukaryotes
In loose strands the majority of the time
Condenses into chromosomes prior to division
Centromere
Where sister chromatids (pairs) are attached and microtubules bind
How many PAIRS of chromosomes are in your nucleus?
23 PAIRS
22 autosomal (homologous)
1 sex pair
Mitosis
Exact copies of original cell
Everywhere but sex cells
Growth and repair of our bodies
Interphase
Most time spent here
Loose DNA strands
DNA replicates (2 copies of each strand in nucleus)
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Prophase
DNA condenses into chromosomes
Microtubules form anchored by centrioles
Nuclear envelope begins to break down
Metaphase
Chromosomes align at the middle
Anaphase
Pulling apart of the sister chromatid to opposite sides of the cell
(Both new cells will have same DNA)
Telophase
Nuclear envelope reforms
Chromosomes unravel
Cytokinesis
Splitting of one cell into two
Pronto-oncogenes
Mitosis regulated by this
If they mutate, they no longer function properly, resulting in cancer
Causes of cancer
Inherited mutations
(BRCA 1/BRCA 2=breast cancer)
Environmental carcinogens
(Smoking, UV radiation, HPV virus)
Malignant
Tumor invades surrounding tissue
Cancerous
Metastatic
Individual cells break off and start a new tumor elsewhere
Cancerous
Benign
Tumor has no effect on surrounding tissue
Non cancerous
Treating cancer
Surgery
Chemotherapy
Radiation
(Vaccines being developed)
Meiosis
Cell division in sex cells
4 cells
Not identical to original
Half the DNA of the original
Interphase (same as mitosis)
Copies of DNA
2 in each cell
Prophase 1
Chromosomes and chromatid joins at centromere
**crossing over happens here-some chromatids (single strands) with have DNA from both mom and dad
Metaphase 1
Homologous chromosomes pair up and randomly align in the middle of the cell
Anaphase 1
Homologous chromosomes pulled towards the ends of the cell
**pairs here NOT just strands of DNA
Telophase 1/Cytokinesis
Nuclear envelope reforms
Chromosomes unravel into loose strands
Cell splits
Prophase 2
DNA condenses
**No crossing over this time
Metaphase 2
Chromosomes align in the middle of the cell
Anaphase 2
Sister chromatids are pulled pulled apart, splitting the pair
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
Heterozygous
Two different alleles of a gene
Homozygous
Same allele of a gene
Dominant
One expressed in a heterozygote
Recessive
Not expressed in a heterozygote
**expressed in a homozygote
Codominance
Both alleles expresses equally but separately
Incomplete dominance
Both alleles expressed but the phenotype is intermediate
Genotype
Genetic composition of an individual (ex. Bb)
Phenotype
The traits expressed by an individual (ex. Brown eyes)
Phenotypic plasticity
Same genotype, different phenotype
Phenotype is determined by:
Genotype AND environment
Mendel (1865)
Work with pea plants is the foundation for genetic inheritance
Mendel’s laws of inheritance
- Segregation-alleles separate from each other during meiosis
- Independent assortment-alleles of different genes are inherited independently of each other
- Dominance-some alleles of a gene may be dominant over others
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
Genes on the same chromosome are often linked
Genes on DIFFERENT chromosomes aren’t linked
DNA replication
Occurs in interphase and inside the nucleus
DNA replication
Step 1: DNA double helix is unwound by he enzyme Helicase
Step 2: DNA polymerase adds nucleotides complimentary to the original strand
DNA replication is semiconservative:
Resulting DNA double helices contain one original strand and one new strand
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
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
Recessive, disease causing alleles on the X chromosome are more harmful in males
XX-healthy
Xx-healthy carrier
xx-hemophilia
XY-healthy
xy-hemophilia
Only 1 X chromosome is “activated” per cell in females
Barr body is the inactivated X chromosome
Sex chromosomes cross over in the PAR regions: the ends
Both X to X and X to Y
Biological sex
Phenotype base in the combination of chromosomes, hormones, and sex organs
Gender
Personal and cultural identity pertaining to biological sex and other factors
Transgender
A person whose gender differs from the biological sex they were assigned at birth
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
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
Sequential hermaphroditism
Being able to change sex during the lifetime (clownfish)
Platypuses have 10 sex chromosomes
Males: XYXYXYXYXY
Females: XXXXXXXXXX
Similar to platypus autosome 6
Birds and butterflies have a ZW sex chromosome system
ZZ-male
ZW-female
Honey bees
Diploid: females
Haploid: males (essentially unfertilized gametes)
Plants
Most are hermaphrodites: both parts on same plant
Some are dioecious: parts on separate individuals (poison ivy and papaya)
Tetrahymena
Have seven different sexes
Why did separate sexes and sex chromosomes evoke?
Separate sexes prevents self fertilization and increases genetic diversity
How did sex chromosomes evolve?
Autosomes—->sex chromosomes
Transcription
Production of mRNA (AUGC)
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
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)
GMO:
Organisms whose genome have been engineered, often incorporating genes from another organism
~80% of all processed foods contain at last one GMO
Corn, soybeans, cotton, potatoes, papayas, apples
Roundup ready soybeans:
Contain gene from bacteria, which confers resistance to the herbicide Roundup
Bt corn
Contains gene from bacteria, which produces toxin against the corn borer insect
Upsides of GMO crops
Produce more food
Potential downsides
$$
Farmers can only use gmo’d seeds for one harvest
GMO medicines
GMO insulin-produced by yeast or bacteria, first GMO medicine
GMO blood clotting proteins (made by goats)
Gene therapy (GMO humans) vs CRISPR
Insertion of gene into harmless virus
CRISPR much more specific than virus method
Stem cells
Undifferentiated cells that have not yet acquired a specific function
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
Cerebellum
Balance, coordination, muscle memory
Thalamus
Relay center for sensory signals except smell
Amplifies or suppresses signals before they go to cerebrum
Limbic system
Hypothalamus
Amygdala
Hippocampus
Hypothalamus
Control center for temperature regulation, blood pressure, thirst, sex drive, emotion
Hormone production
Pituitary gland
Amygdala
Fear, pleasure, emotional response
Flight/flight
Hippocampus
Learning
Short term memory
Cerebrum
Planning, creativity, consciousness, voluntary movement, language
Four lobes
Frontal-higher thinking
Parietal-touch
Occipital-visual information
Temporal-auditory information
Brain hemispheres
Control the opposite sides of the body
Corpus callosum
Connects the hemispheres
Cerebrospinal fluid
Cushions and protects the bran from the skull
Concussions
Cause shock, headache, confusion
Can cause irritability, trouble sleeping, depression, brain damage
Woodpecker traits that reduce concussions
Less cerebrospinal fluid
Spongy bone layer and hard, elastic bone layer (to absorb impact)
Can get brain damage
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
Central nervous system
Brain and spinal cord
Peripheral nervous system
Nerves radiating through the rest of the body
Neurons
Specialized cells that carry messages in the brain and nervous system
Sensory neurons
Carry information from the body to the CNS
Motor neurons
Carry information AWAY from the CNS towards the rest of the body
Anatomy of a neuron
Dendrites Cell body Axon Terminal boutons (Nerves are bundles of axons)
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
How does a nerve impulse travel from one neuron to the next?
Synapse: a junction between two neurons
Neurotransmitters
Transmit the signal between neurons at the synapse
Removal of neurotransmitters from synapse
Reuptake into pre-synaptic neuron through channel OR digestion by enzymes in the synapse
Rene Descartes
Mathematician
Proponent of rational thinking regarding the natural world
Believed that the pineal gland contains the human soul
Phrenology
Pseudoscience claiming the shape and size of the skull indicates a person’s personality and abilities
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
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
