Plants & Society Exam III

What is genetics?

The study of inheritance

What is Homozygous?

Having the same genes in a pair; identical alleles

What is Heterozygous?

having unlike genes in a pair; two different alleles

What is a Phenotype?

An expression of genes present; physical traits

What is a Genotype?

the actual genes present

List 3 characteristics of early awareness of inheritance.

1. traits are passed from parents to offspring
2. Artificial selection was practiced by farmers
3. today we have clear understanding of the nature of genes and the scientific basis for selective breeding

List 4 characteristics of Genes.

1. hereditary material (DNA) found in chromosomes
2. organized in units (a segment of DNA molecule)
3. Each gene codes for the formation of one protein
4. Genes control all phases in the life of an organism

Where do genes occur?

chromosomes (at a specific location); on the homologous chromosome, there is a second gene for the same trait at the same location

What are Homologous chromosomes?

look alike and carry genes for the same traits

What are Gametes?

haploid and contain 1 of each homologous chromosome

What happens to the zygote?

receives one haploid set of chromosomes from egg and one set from the sperm

For any genetic trait, organisms have 2 genes. It will receive...

one gene on a specific chromosome from one parent and another gene for that same trait on the homologous chromosome from the other parent

What are Alleles?

1. alternate forms of a genes
2. gene that controls flower color may have alleles that specify purple or white flowers

What are dominant traits?

Each trait one allele generally masks/is dominant over the other

What are recessive traits?

non dominant allele

Who is the father of genes?

Gregor Mendel (19th century); Augustinian monk who lived and worked in an Austrian monastery

Why was Mendel's work ignored?

it was no mainstream; too brilliant; hard to understand

Summarize Mendelian Genetic findings.

experiments with garden peas that demonstrated the principles of heredity; garden peas easy to work with (self pollinate but easy to cross)

List the 7 contrasting pairs of traits from Mendel and the Garden Pea.

Mendel selected seven contrasting pairs of traits:
Tall versus dwarf plants
Yellow versus green seeds
Round versus wrinkled seeds
Green versus yellow pods
Inflated versus constricted pods
Purple versus white flowers
Terminal versus lateral flowers

What is monohybrid crossing?

Mating individuals that differ in only one trait

What was the offspring of the cross called, and what did they produce?

F1 generation, or first filial generation; produced yellow seed

F2 generation, or second filial generation

1. Approximately 3/4 yellow and 1/4 green
2. 3:1 ratio

What are the 3 Molecular basis of heredity?

1. how traits are passed from one generation to another
2. Understanding nucleic acids and what they do
3. explains how genes function

What are Nucleic Acids?

chemical compounds composed of repeating units called nucleotides

List 3 basic units of the DNA molecule.

1. one sugar (either ribose or deoxyribose)
2. one phosphate group (PO4)
3. one nitrogenous base

List the 2 Nitrogen (Purine) bases

*adenine (A)
*guanine (G)

List the 3 Nitrogen (Pyrimidine) bases

*cytosine (C)
*thymine (T) only in DNA
*uracil (U) only in RNA

What is DNA?

*hereditary material
*sequence of the bases in DNA makes up the genetic code
*often called the double helix (double stranded molecule twisted into a helix)
*Pairs of bases extend across
A=T, G=C

What are the sides of a DNA helix composed of?

sugars and phosphates

What is RNA?

*Single stranded
*manufacture of proteins by carrying out the instructions coded on the DNA molecule

What are the differences between RNA and DNA?

1. DNA is Double stranded while RNA is Single Stranded
2. DNA is a double helix while RNA is a single helix
3. DNA has Deoxyribose sugar while RNA has ribose sugar
4. DNA stores and transmits genetic information while RNA acts as a template for making proteins.
5. DNA is found in the nucleus only. RNA is found everywhere in the cell
6. There is only one kind of DNA. There are three kinds of RNA--tRNA, mRNA, rRNA

List the 3 Types of RNA

1. mRNA=messenger RNA
2. rRNA = ribosomal RNA
3. tRNA = transfer RNA

What is a Transcription?

synthesis of an RNA molecule from a DNA template:
1. mRNA carries information for a protein out to the cytoplasm
2. mRNA attaches to a ribosome

What does the DNA do during transcription?

1. part of DNA molecule unwinds
2. One strand serves as template for synthesis of mRNA
3. molecule of DNA rewinds and mRNA leaves the nucleus

What are 4 characteristics of Genetic Code?

*Every 3 bases on the RNA is called a codon
*Each codon specifies an amino acid
*universal
*In the cytoplasm, the mRNA attaches to a ribosome

What is a Translation?

1. mRNA molecule is translated into a protein
2. mRNA molecule is read codon by codon to form a chain of amino acids
3. Amino acids are carried to the ribosome by tRNA

What happens to the amino acid as the mRNA is translated?

the amino acid chain elongates

What are 3 characteristics of the Universal Code?

*Genetic code and protein synthesis is the same in all living organism
*One organism can understand the genetic instructions of another organism Universal code
*Using tools of genetic engineering scientists can transfer genes from one organism to another

What classifies as a macronutrient? (3)

carbohydrates, proteins, and fats (required in large amounts)

What is a Calorie?

*A measure of energy
*The amount of energy to raise the temperature of one gram of water one degree Celsius

List the three types of Carbohydrates

1. Monosaccharides
2. Disaccharides
3. Polysaccharides

Define Monosaccharides and list the 3 parts

*Simple sugars
*Building block of more complex carbohydrates

1. Glucose (abundant)
2. Fructose
3. Galactose

Define Disaccharides and list the 3 parts

Two monosaccharides chemically joined

1. Sucrose
2. Lactose
3. Maltose

What is sucrose and the formula?

glucose + fructose

What is lactose and the formula?

1. Milk Sugar
2. glucose + galactose

What is maltose and the formula?

*glucose + glucose
*germinating grains

Define Polysaccharides and give 3 examples.

*complex carbohydrates
*hundreds to thousands of sugar units
*Glucose is the only monosaccharide
*Distinguished by the way in which the glucose units are joined together, their arrangement, and their number

1. Starch
2. Glycogen
3. Fiber (cellulose)

How is Glucose made and how is it transported?

*During digestion, other carbohydrates are broken down or converted to glucose
*Transported by the blood to all the cells in the body *Within cells, respiration breaks down glucose to produce energy necessary to sustain life

What is Fructose and Galactose?

*both monosaccharides
*same chemical make up as glucose, C6H12O6, differing only in the arrangement of the atoms
*Converted into glucose and metabolized
*High fructose corn syrup (sweeter than sucrose)

What is Starch?

*Storage form of glucose found in plants
*Seeds, some fruits, tubers, and tap roots
*Starch in foods can be traced directly to plant origin: starch in bread or pasta from wheat

Examples of Starches in Human Diet

*Grains (wheat, rice, and corn)
*Underground crops (potato, sweet potato, & cassava) *Legumes (beans and peas)

How and what are starches broken down to?

*broken down to glucose by enzymes in saliva/small intestine
*transported by blood to body cells

Where is Glycogen found and not found?

*liver and skeletal muscles
*excess glucose--stored as glycogen
*only 1 day's worth of glycogen stored
*not in plants

What is carbohydrate loading?

*eat lots of starchy foods to build glycogen reserves
(excess glucose stored as fat)

List 3 characteristics of Fiber (polysaccharide)

*from plants
*not digestible
*provides bulk

What are sources of fiber?

1. fruits
2. veggies
3. seeds
4. whole grain

List the types of dietary fibers (7)

1. cellulose
2. lignin
3. hemicellulose
4. pectin
5. gums
6. mucilages
7. other

What is Cellulose (fiber)?

*principal component of plant cell walls
*made of glucose
*humans can't break it down--passes through digestive system as roughage

What are Pectins (fiber)?

*cell wall polysaccharides
*middle lamella

What are Hemicelluloses (fiber)?

*cell wall polysaccharides

Where do you find Gums and mucilages?

*exudates from plants
*also thickening agents

What are another dietary fiber from polysaccharides?

red and brown algae

Give examples of Insoluble fibers and list the benefits.

1. Cellulose (wheat bran)
2. Lignin
3. Some hemicelluloses

*speeds up passage of food through large intestine
*reduces risk of colon cancer

Give examples of Soluble fibers and list the benefits.

1. algal polysaccharides
2. gums (oat bran)
3. mucilages
4. pectins (apples)
5. other hemicelluloses

*lowers cholesterol

List 4 characteristics of Protein.

*large complex molecules
*composed of amino acids
*structural components
*regulate bodily functions

How many naturally occurring amino acids are there?

20

How are the proteins in our food digested?

broken down into amino acids by enzymes in the digestive tract and transported in the blood stream

What is the role of dietary protein?

*to supply amino acids for the body to make human proteins
*All 20 amino acids are necessary for protein synthesis

How many amino acids can the human body synthesize?

11

What are the 3 Essential Amino Acid Characteristics

*Cannot be stored by the body
*must be present simultaneously in the diet
*need all in each meal

What are the essential amino acids? (9)

1. Histidine
2. Isoleucine
3. Leucine
4. Lysine
5. Methionine
6. Phenylalanine
7. Threonine
8. Tryptophan
9. Valine

What are the nonessential amino acids? (11)

1. Alanine
2. Arginine
3. Asparagine
4. Aspartic acid
5. Cysteine
6. Glutamic acid
7. Glutamine
8. Glycine
9. Proline
10. Perine
11. Tyrosine

What are Complete Proteins?

*contain all 9 essential amino acids
*most proteins derived from animals

What are Incomplete Proteins?

*plant proteins
*lack 1 ore more essential amino acid

What are Complementary Plant Proteins? Give some examples

*combining complementary plant proteins that can supply all E.A.A.
*beans and corn

What essential amino acids are beans low/high in?

*low in methionine
*high in tryptophan and lysine
*contains complementary proteins

What essential amino acids is corn low/high in?

*low in lysine and tryptophan
*high in methionine
*complementary plant proteins

What is Malnutrition?

quality deficiency in which 1 or more essential nutrients is lacking even though there's enough calories

What is Undernutrition?

insufficient calories to maintain energy requirements

What are Fats (lipids)?

*organic molecules
*diverse group of compounds
*insoluble in water

List 3 types of fats.

1. Triglyceride
2. Steroid
3. Phospholipid

What are Tryglycerides and how are they formed?

*95% of lipids in foods - fats and oil
*Formed from glycerol and 3 fatty acids

List 5 characteritics of Fatty Acids

*simplest form of lipids
*building blocks for triglycerides and phospholipids
*carbon chain w/ hydrogen attached
*body can synthesize most fatty acids
*number of carbon and hydrogen atoms varies

What are the 3 fatty acids that must be supplied by the diet?

1. Linoleic acid
2. Linolenic acid
3. Arachidonic acid

What are the types of fatty acids?

1. Saturated: all single bonds between carbon atoms
2. Unsaturated: have one or more double bonds

List 3 characteristics of Saturated Fats.

1. mostly saturated fatty acids
2. solid at room temperature
3. animal fats such as lard, butter, and beef fat

What are some characteristics of Vegetable Oils.

1. mostly unsaturated fatty acids
2. liquid at room temperature

What are some vegetable oils with monounsaturated fatty acids

1. olive oil
2. peanut oil
3. canola oil

What are some vegetable oils with polyunsaturated fatty acids

1. corn oil
2. soybean oil
3. safflower oil

Give 3 examples of saturated fats in plants

1. coconut oil
2. palm oil
3. cocoa butter

What is Hydrogenation?

*addition of hydrogen to make an unsaturated oil, a saturated fat
*converts a liquid oil into a solid fat - margarine
*unsaturated oil has been chemically modified by hydrogenation

What are the bad effects that diets high in saturated fats lead to?

*colon, breast, and prostate cancers
*blood cholesterol levels-linked to cardiovascular disease

What are the good effects that diets high in unsaturated fats have lead to?

*lower blood cholesterol levels
*lower the risk of cardiovascular disease

What is cholesterol? What is it used for?

*steroid
*4 carbon rings
*part of lipid component of cell membranes
*used in the synthesis of sex hormones and more
*Insoluble in the watery medium of blood

What are trans fats?

*unsaturated fat with transisomer
*raise cholesterol levels/cardiovascular disease

Where is cholesterol made?

synthesized in liver from saturated fatty acids and absorbed by intestinal cells from animal foods

List examples of food sources that contain cholesterol.

*eggs, butter, cheese, meat
*high saturated fats=increased cholesterol synthesis

What are the 2 types of Lipoproteins (lipids and proteins)?

*transported molecule
*Low-density lipoproteins (LDLs)
*High-density lipoproteins (HDLs)

What are the bad effects of Low-density lipoproteins (LDLs)?

*bad cholesterol, causing deposits in arteries and leading to heart attacks and strokes
*transport cholesterol - all body cells

What are the good effects of High-density lipoproteins (HDLs)?

*remove excess cholesterol- body tissue
*carry to liver for degradation and elimination
*good cholesterol