Semester 2 Final

What happens to an organism's cells when it grows?

Cells increase in number through cell division (mitosis) to allow tissues and organs to grow.

Why do cells tend to be small?

Cells tend to be small due to the surface area-to-volume ratio; smaller cells transport nutrients and waste more efficiently.

What are the three main stages of the cell cycle?

1. Interphase: cell growth and DNA replication. 2. Mitosis: division of the nucleus. 3. Cytokinesis: division of the cytoplasm.

What happens during interphase? How many phases are there and explain them.

The cell grows (G1 phase), replicates its DNA (S phase), and prepares for division (G2 phase)

What are the 4 stages in mitosis?

Prophase (chromosomes condense and become visible, the nuclear envelope breaks down, and the spindle fibers form; Metaphase (chromosomes line up along the metaphase plate, and spindle fibers attach to the centromeres; Anaphase(sister chromatids separate and move to opposite poles of the cell); Telophase (chromosomes decondense, the nuclear envelope reforms, and the solidly fibers disappear)

What is the composition of chromosomes?

Chromosomes are composed of DNA tightly wound around proteins called histones.

Differentiate between chromosomes and chromatin.

Chromosomes are the condensed form of DNA during cell division, while chromatin is the less condensed form present during interphase.

Describe the structure of chromosomes.

Chromosomes consist of two identical sister chromatids attached at a central region called the centromere.

What happens during prophase of mitosis?

Chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and spindle fibers form.

What are the main events of anaphase in mitosis?

Sister chromatids separate and move to opposite poles of the cell.

What are the main events in telophase?

Chromosomes arrive at the poles and begin to decondense, the nuclear envelope reforms around each set of chromosomes, solidly fibers disappear

Describe the process of cytokinesis.

Cytokinesis is the division of the cytoplasm; in animal cells, it involves the pinching of the cell membrane, while in plant cells, a cell plate forms.

What are cyclins?

Cyclins are proteins that regulate the cell cycle by activating cyclin-dependent kinases (Cdks) to promote cell division.

Identify the G1 checkpoint.

The G1 checkpoint checks for DNA damage, cell size, and nutrient availability before entering S phase.

What is the S checkpoint?

Ensures that DNA replication is proceeding correctly

What is the G2 checkpoint?

Checks for DNA damage and ensures that DNA replication is complete before entering mitosis

What is cancer?

Cancer is characterized by uncontrolled cell growth and division, which can invade and damage surrounding tissues.

Define carcinogens.

Carcinogens are substances that can cause cancer, including certain chemicals, radiation, and viruses.

What is apoptosis?

Apoptosis is programmed cell death, which occurs to eliminate damaged or unnecessary cells.

What are stem cells?

Specialized cells with the ability to self renew and differentiate into various cell types

Differentiate adult and embryonic stem cells

Adult stem cells are multi potent or unipotent, meaning they can only differentiate into a limited set of cell types within their tissue of origin; embryonic stem cells are pluripotent, meaning they can ebcome any cell types within their in the body

What are homologous chromosomes?

Homologous chromosomes are pairs of chromosomes that contain the same genes but may have different alleles.

What is a diploid number?

A diploid cell contains two sets of chromosomes; in humans, the diploid number is 46.

What is a haploid cell?

A cell containing one set of chromosomes (n). In humans, the haploid number is 23. These are found in gametes

What occurs during prophase I of meiosis?

Chromosomes condense, homologous chromosomes pair up, and crossing over occurs.

Prophase I

Chromosomes condense, and homologous chromosomes pair up, forming tetrads. Crossing over occurs, exchanging genetic material between homologous chromosomes.

Metaphase I

Tetrads line up along the metaphase plate. Spindle fibers attach to the centromeres of homologous chromosomes

Anaphase I

Homologous chromosomes separate and move to opposite poles of the cell. Sister chromatids remain attached

Telophase I

Chromosomes arrive at the poles, and the cell divided, resulting in two haploid daughter cells

Meiosis II

Separates sister chromatids (similar to mitosis)

Prophase II

Chromosomes condense

Metaphase II

Chromosomes line up along the metaphase plate. Spindle fibers attach to the centromeres of sister chromatids

Telophase II

Chromosomes arrive at the poles, and the cell divided resulting in four haploid daughter cells

What is independent assortment?

The principle that alleles for different traits are inherited independently of one another.

What is the difference between asexual and sexual reproduction?

Asexual reproduction involves one parent producing identical offspring, while sexual reproduction involves two parents creating genetically unique offspring.

Crossing Over

Exchange of genetic material between homologous chromosomes during meiosis

Independent Assortment

Random distribution of chromosomes during meiosis

Random Fertilization

Any sperm can fertilize any egg, leading to different combinations of genes

Explain how the process of meiosis produces genetic recombination

Meiosis produces genetics recombination through crossing over and independent assortment

Gene linkage

Genes that are located close together not he same chromosomes tend to be inherited together. This is because they are less likely to be separate during crossing over

Polyploidy

A condition in which an organism has more than two sets of chromosomes (ex 3n, 4n)

What is the importance of of polyploidy in agriculture?

Polyploidy can lead to increased size and vigor in plants. Many important crops, such as wheat and potatoes, are polyploidy. Polyploidy can also lead to new species formation

What did Mendel’s experiments enable him to realize?

Traits are inherited as genes and some traits are dominant over others

Dominant genetic disorders

Require only one copy of the dominant allele to be present for the disorder to be expressed

Recessive genetic disorder

Require two copies of the recessive allele to be present for the disorder to be expressive

Which of the following is not recessive genetic disorder?

A. Cystic fibrosis

B. Sickle cell anemia

C. Tay-Sachs disease

D. Huntington disease

D

Alleles

Different versions of a gene

Dominance

When two different alleles are present, the dominant allele is expressed, and the recessive allele is masked

Law of Segregation

During gamete formation, the two alleles for each trait separate, so that each gamete carries only 1 allele for each trait

Punnent squares

Used to predict the genotypes and phenotypes of offspring from a genetic cross. For a monohybrid cross (involving one trait). Dihybrid cross involves two traits

What is natural selection?

Natural selection is the process where individuals with advantageous traits are more likely to survive and reproduce.

Explain gene linkage.

Gene linkage refers to genes that are located close together on the same chromosome and tend to be inherited together.

What is polyploidy?

Polyploidy is the condition of having more than two sets of chromosomes, which is important in agriculture for crop improvement.

What are dominant genetic disorders?

Genetic disorders that require only one copy of a dominant allele to be expressed, such as Huntington’s disease.

What are recessive genetic disorders?

Require two copies of the recessive allele to be present for the disorder to be expressed (cystic fibrosis, sick cell anemia)

Square

Male

Circle

Female

Shaded symbols

Individuals with the trait

Horitzontal lines connect….; vertical lines connect…

Parents; parents to offspring

Roman numerals indicate

Generations

Complete dominance

One allele completely masks the expression of the other allele

Explain incomplete dominance.

A genetic scenario where the heterozygous phenotype is a blend of both homozygous phenotypes.

What is epistasis?

Epistasis occurs when one gene masks or modifies the expression of another gene.

Polygenic inheritance

Traits that are determines by multiple genes (skin color, height)

Identify environmental factors that influence gene expressions and phenotypic traits

Nutrition, temperature, exposure to toxins

Twin studies

Used to study the relative contributions of genetic and environmental factors to phenotypic variation

Karoytype

An individuals set of chromosomes

Nondisjunction

Failure of chromosomes to separate properly during meiosis, leading to gametes with abnormal chromosomes numbers

What is the cause of Down syndrome?

Caused by trisomy 21, an extra copy of chromosomes 21

Identify chromosomal disorders in sex chromosomes

Turner syndrome; Klinefelter syndrome

Turner syndrome

Females with only one X chromosome

Klinefelter syndrome

Males with an extra chromosome

Functions of DNA

Stores genetic info, directs protein synthesis, undergoes replication to pass genetic information to daughter cells, capable of mutation, allowing for genetic variation and evolution

Nucleotides

Sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base

Double helix model

• DNA consists of two strands wound around each other in a double helix

• The sugar-phosphate backbone forms the sides of the helix

• Nitrogenous base (adenine, guanine, cytosine, and thymine) from the rungs of the helix

• Base pairing: adenine Paris with thymine (A-T) and guanine pairs with cytosine (C-G)

Rosalind Franklin

Used x-ray diffraction to produce images of DNA, which provided crucial info about its structure

Watson And Crick

Used Franklin’s data, along with their own, to develop the double-helix model of of DNA

DNA replication

The process by which DNA is copied

• DNA unwinds and separates into two strands

• Each strand serves as a template for the synthesis of a new complementary strand

• DNA polymerase adds nucleotides to the new strand, following base-pairing rules (A with T, and G with C)

Prokaryotic cells

Replication occurs in cytoplasm

Eukaryotic cells

Replication occurs in the nucleus

Sugar DAN vs RNA

Contains deoxryribose, ribose

The role of RNA

Carrying genetic information from DNA to ribosomes (mRNA), serving as a structural component of ribosomes (rRNA), and carrying amino acids to the ribosome during translation (tRNA)

Messenger RNA, carries genetic information form DNA to the chromosomes

mRNA

Ribosomal RNA, forms part of the structure of ribosomes

rRNA

Transfer RNA, caries amino acids to the ribosome during translation

tRNA

Describe how the cell makes RNA in transcription

RNA polymerase binds to DNA and separates the strands; RNA polymerase synthesizes a complementary RNA strand, using one strand of DNA as a template; The RNA strand is released, and the DNA strands rejoin

Describe the process of translation

• mRNA binds to a ribosome

• tRNA molecules, each carrying a specific amino acid, bind to the mRNA codons via their anticodons

• The ribosome moves along the mRNA, adding amino acids to the growing polypeptide chain

• The process continues until a stop codon is reached, and the polypeptide chain is released

Define mutation.

A mutation is a change in the nucleotide sequence of DNA.

Types of mutations

Point mutations substitution, insertion, deletion, frame shift mutations

Point mutations

Chained in a single nucleotide

Substitution

One base is replaced by another

Insertion

An extra base is added

Deletion

A base is removed

Frameshift mutation

Insertions or deletion that alter the readings from of the mRNA

Credited with developing the theory of revolution by natural selection. He proposes that species change over time through a process in which individuals with advantageous traits are more likely to survive and reproduce

Charles Darwin

His worker on ecology suggested tht Earth is very old and changes gradually ove time

Lyell

Proposed the idea of inheritance of acquired characteristics, which Darwin initially considered but later focused on natural selection

Lamarck

Argued that population growth faster than resources, leading to competition and struggle for survival, which influenced Darwin’s concept of natural selection

Malthus

The process by which humans selectively breed plants and animals for desired traits. This demonstrates that traits can change over time through selective breeding

Artificial selection

What are the four principles of natural selection

Excess production (organisms produce more offspring than can survive), variation (individual within a population exhibit variation in their traits), inheritance (traits are inherited from parents to offspring), and advantages of certain traits (fitness)(individuals within advantageous traits are more likely to survive and reproduce in certain environments)