Ch3 Heredity and Evolution Flashcards Preview

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Flashcards in Ch3 Heredity and Evolution Deck (26)
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1

Cells
1. Specialized
2. Stem
3. Prokaryotic
4. Eukaryotic

1. Specialized cells
- tissue cells (bone, skin, nerve, muscle, blood)
- sex cells (sperm, ovum)
2. Stem cells
- embryonic and adult
3. Prokaryotes (lack nucleus)
- Earliest organisms 3.7 billion years ago (bya)
- Most diverse and successful life form today
4. Eukaryotes (have nucleus)
- Arose1.5-1.0 bya
- Gave rise to multicellular organisms

2

Meiosos

Production of sex cells (gametes) via two cell divisions = four daughter cells
- Haploid: single set of unpaired chromosomes
- 23 single-stranded chromosomes

3

Mitosis

Division of somatic cells resulting in production of two daughter cells
- 23 double-stranded
- 46 single-stranded chromosomes

4

The Building Blocks of Life (6)

1. Nucleotides
2. Double Helix
3. Gene
4. Chromosome
5. Nucleus Functional Human

5

Gene

- A sequence of DNA (or RNA) that codes for a molecule that has a function
- Will always have 2 copies

6

Chromosome

- A chromosome consists of a long strand of DNA containing many genes
- A human chromosome can have up to 500 million base pairs of DNA with thousands of genes

7

To Make a Protein

RNA
- single-stranded, uracil instead of thymine, different sugar
mRNA
- transcription
tRNA
- translation

8

Gregor Mendel

1866 paper “Experiments in Plant Hybridization”
- Inheritance in pea plants
- Considered father of genetics

Genetics + Natural Selection = The Modern Synthesis
- Discrete or Mendelian traits: present or absent
- Phenotype or genotype

9

Alleles

- Alternate forms of a gene that occur at the same locus on homologous chromosomes
- Dominant versus Recessive
- Homozygous vs. Heterozygous

10

Allele Misconceptions

- Dominant alleles are not “stronger”, “better” or more common
- Often they are quite rare (Huntington disease)

11

Environmental factors on traits

- Genotypes set limits, but also interact with the environment
- Phenotypic expressions are affected by this interaction
- Ex. Height is determined by genes, but childhood nutrition and development can affect height

12

Punnett Square

- Can use to determine if alleles are:
homozygous ‘TT’ or ‘tt’
heterozygous ‘Tt’

13

Monogenic Traits

- Controlled by a single gene
- Co-dominance, e.g. ABO blood system

14

Principles of Inheritance:
Segregation

- each sex cell contains only one allele from each parent
- Genes occur in pairs because chromosomes appear in pairs

15

Independent Assortment

- Distribution of one pair of alleles into the sex cells does not influence the
- Ex. The colour of your hair does not affect the colour of your eyes
- Genes controlling different traits are inherited separately from one another

16

Examples of Sex- Linked genes

Sex linked genes on the X chromosome
- Red-green colour blindness
- Hemophilia
More than 20, 000 inheritable traits

17

Modern Synthesis

Synthesis of Mendelian genetics and natural selection within evolutionary theory

18

Evolution as a 2-stage Process

1. Production and redistribution of variation
2. Natural selection acting on this variation
- inherited differences among individuals differentially affecting their ability to successfully reproduce

19

Variation: Mutations

- Alteration to a gene or chromosome
- Can be caused by exposure to chemicals, radiation, and sunlight
- Can be neutral, beneficial or harmful
- Only passed on if occur in the sex cells

20

Variation: Gene Flow

- Exchange of genes between populations
- Occurs only when migrants interbreed
- Ex. African-Americans are largely of West African decent, but due to gene flow, they are estimated to have 20-25 percent of their gene pool come from non-African decent

21

Variation: Genetic Drift

‘Random’ factor in evolution and occurs in small populations
- Common example is founder effect: allele frequency alteration in small populations that are remnants of larger populations
- May cause a genetic bottleneck - loss of genetic diversity

22

Recombination

- Occurs during meiosis
- Important source of variation
- When genetic material is exchanged between homologous chromosomes
- Happens in the beginning, they switch genes and alleles before meiosis begins

23

Nondisjunction

- Failure of a chromosome to separate properly during meiosis
- Results in more or less than normal number of chromosomes
- Trisomy (e.g. Down syndrome)
- Monosomy (e.g. Turner syndrome)

24

Sickle Cell Anemia
(Via alleles)

- Most humans are homozygous HbA/HbA and they produce normal hemoglobin
- Worldwide the HbS allele is very rare
- People who are heterozygous HbA/HbS have a condition called *sickle-cell trait*
- People who are homozygous HbS/HbS have a condition called *sickle-cell anemia*

25

Sickle Cell Anemia
(Symptoms/ stats)

• Cause red blood cells reduced ability to transport oxygen through the blood stream
• Cause difficulties while exercising because of lack of oxygen
• Can clump together and block capillaries
• 100,000 deaths per year world wide
• 40-50,000 individuals (mostly African descent) in USA suffer from this condition

26

Malaria
(symptoms and stats)

- Kills 1-3 million people every year
- The parasite invades red blood cells, where they get the oxygen they need for reproduction
- Fever, headache, chills, nausea, vomiting and frequently death
- In parts of western and central Africa, 50-75% of 2-9 year olds are affected
- People with sickle cell anemia have a higher resistance to malaria