DNA and Genetics

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Photosynthesis:

Autotrophs- capture and conversion of sunlight energy into chemical bond energy

Sunlight= the ultimate source of energy

photosynthesis uses light energy to fix carbon dioxide into carbohydrate

CO2 + H2O + sunlight energy --> C6H12O6 + O2

input of new chemical bond energy into biological systems

release of molecular oxygen eventually enabling evolution of oxidative respiration

much more energy available, allows huge increase in number, diversity, complexity of organisms

What do plants do with glucose once it's made?

store it as starch (alpha glucose)

use cellulose as structural support (cell wall)

respiration (ADP -> ATP)

make other macromolecules

Photosynthesis:

Two distinct processes:

Light energy used to generate ATP and NADPH (light harvesting reactions)

ATP & NADPH used to fix CO2 into carbohydrate (enzyme regulated reactions in STROMA = Calvin Cycle)

What is light?

Electromagnetic energy transmitted as waves.

They can move through empty space, unlike sound waves

"light" is electromagnetic energy that we can see

specific wavelengths are perceived as colors

Pigments: absorb specific wavelengths of light; they're compounds not colors

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WAVELENGTHS:

tHE REMAINING WAVELENGTHS REFLECTED OR TRANSMITTED ARE PERCEIVED AS THE PIGMENTS COLOR

Chrolorphylls absorb blue and red light and transmit green light

Carotenoids absorb blue and green light and transmit yellow, orange or red light

Chlorophyll a:

main photosynthetic pigment, embedded in thylakoid membranes

Chlorophyll b:

Accessory pigment. Absorbs different blue and red wavelengths, passes energy to chlorophyll a

Carotenoids:

Accessory pigment. Absorbs blue and green wavelengths. Passes it

absorbs light energy; "excites" electron (jumps briefly to higher orbital)

reradiates a lower energy

All pigments do this

In thylakoids, chlorophyll molecules excited by light transfer absorbed energy (not electrons) other chlorophylls until it reaches reaction center chlorophyll a molecule

When reaction center chlorophyll a receives the energy its excited electron is transferred to an acceptor molecule. The absorbed energy is now chemical energy.

Chlorophylls organized into two kinds of photosystems (1 and 2)

photosystem 2: excited electron fed into an electron transport chain, generating ATP (photophosphorylation)

electron transport pumps protons across thylakoid membrane into lumen

concentrated protons diffuse back out storm through ATP synthase channels, phosphorylating ATP.

Fluorescence: when absorbed light is re-radiated at visible wavelengths

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What happens when replication reaches the end of a molecule?

Leading strand replicated to end

Lagging strand end remains unreplicated, no starting position upstream.

Unxeplicated ends snipped off; chromosome shortened.

Telomeres: are the end portions of eukaryote DNA.

No genes. Tandem repeat sequence.

The unreplicated partied off after each replication cycle.

When entire telomere gone, cell cannot divide further.

Telomere length can determine number of times the cell can divide.

Some cells can continue to divide by restoring telomeres using the enzyme= Telomerase

Has built in RNA template complementary to telomere sequence

Adds nucleotides to end of telomere

Cancer often involves inappropriate telomerase activity

DNA REPLICATION

Replication error: about once per 100,000 nucleotides, DNA polymerase inserts wrong base

DNA Proofreading: DNA polymerase breaks up removing nucleotides, then repeats polymerization

Mismatched repair enzymes: double check replication; recognize and fixes mismatches that DNA polymerase missed.

Excision repair enzymes fix damage to DNA caused by chemicals, UV, etc.

ex: xeroderma pigmentosa

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Meiosis

Special cell division associated with sexual reproduction

Daughter cells have one half the chromosome number of the parent cell.

Life Cycle: course of biological events in an organisms life from one generation to the next

Life cycle= syngamy and meiosis alternate

one full turn of the life cycle= one generation

Asexual Reproduction : one individual self reproduces

offspring are genetically identical to parent

Sexual Reproduction: two individual involved

offspring not identical to either parent

Gametes: cells that fuse in sexual reproduction

syngamy: fusion of gametes

gametes are haploid (one set of chromosome)

zygote: product of fusion

the zygote is diploid

sexual fusion produces a cell with two copies of each chromosome

​​​​​​​each chromosome has a homologous pair

isogamy: compatible gametes are the same size and shape

anisogamy: compatible gametes are different size

oogamy: compatible gametes are different size and shape, only one is motile

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One of the two X chromosomes is always inactivated in somatic cells of female mammals

Which X chromosome becomes inactive Barr Body is random

So females are a mosaic of X chromosome gene expression

The X-O system

Individuals with a single sex chromosome are male; those with 2 copies are female

The Z-W system

Reverse of xy system;

Chromosomal Alterations

Deletion

Duplication

Inversion

Translocation

Extranuclear Inheritance

Mitochondria and plastids have their own DNA

Organelles often inherited maternally: passed down from mother to next generation in cytoplasm of egg cell

HUMANS: Sperm contributes only its nucleus to zygote. Males don't pass mitochondrial genome to next generation

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