bio test

What are the basic units of life?

Cells

How do plant and animal cells compare

whilst plant and animal cells contain similar organelles, they differ as plant cells have features such as a cell wall and chloroplast, as well as a larger vacuole

How do prokaryotic cells differ from eukaryotic cells in size and complexity?

Prokaryotic cells: are smaller and simpler, lack nucleus, genetic info is stored in the nucleoid, and lack membrane bound organelles

Eukaryotic cells: are larger, complex, it has a nucleus and specialised organelles

How do specialised cells relate to their function?

Their structure has adapted to become specific to the role they perform. So the type and number of organelles in the cell, change as needed for it’s function to increase efficiency

Example of specialised cells structure adapting

A sperm cell: It’s purpose is to fertilise an egg - so it has a tail, a lot of mitochondria to provide energy, enzymes in the head to penetrate the egg.

Name key organelles

Ribosomes, nucleus, Mitochondria, Chloroplasts, cell membrane.

What is the function of the nucleus?

It stores genetic material (DNA) and controls cell activities

role of ribosomes

Where protein is made

role of the Mitochondria

Where energy/ATP is produced through cellular respiration

role of chloroplast

Carry out photosynthesis which converts light energy into chemical energy in plant cells

role of the cell membrane

control what enters and exits the cell, as well as a protective outer boundary of the cell.

How do organelles interact in larger biological processes?

Organelles work together in coordinated pathways, each organelles performs a specific role which contributes to an overall cellular process

examples of cells working together in a larger biological process

In the exocytosis of proteins, the DNA in the nucleus holds the instructions for protein synthesis. Ribosomes use these instructions to produce proteins. The rough ER folds the protein. The protein is sent to the golgi apparatus to be modified, sorted and package into vesicles. The vesicles fuse with the cell membrane and release protein outside the cell.

What doe diploid and haploid mean in terms of chromosome number?

Diploid: 2n is when a cell has 2 sets of chromosomes one from each parent - 46

Haploid: n is when a cell has 1 set of chromosomes

Main purpose of Mitosis

for growth, repair, replacement and asexual reproduction

What does Mitosis produce

Produces two identical diploid daughter cells

What is the phases of Mitosis

Prophase

Metaphase

Anaphase

Telophase

What are the 2 other essential stages of the cell cycle

Interphase

Cytokinesis

Interphase - mitosis

G1 - cell grows and produces proteins and organelles

synthesis - DNA replication - sister chromatids

G2 - Further growth, prepares machinery for mitosis

Prophase - mitosis

• Chromatin condenses into visible chromosomes - each chromosome consist of two sister chromatids

• Nucleus disappears

• Spindle fibers form from microtubules and attach to centromeres

Metaphases - mitosis

• Chromosomes line in the equator of the cell - spindle fibers attached to the centromere pull the chromosomes into alignment

• arranged so each chromatid is attached to spindle fibers from opposite poles

Anaphase - mitosis

Sister chromatids are separated at the centromere by spindle fibers

The spindle fibers shorten and pull the chromosomes in opposite directions

Cell elongates as microtubes pull poles apart

this process ensures each daughter cell receives identical sets of chromosomes

Telophases - mitosis

Chromosomes reach the opposite poles

The chromosomes decondense into chromatin

Nuclear envelope form around each set

Nucleolus reappears in each new nucleus

spindle fibers disappear

prepares for cytokinesis.

Cytokinesis - mitosis

The division of the cytoplasm, which divides the parent cell into two identical daughter cells

How does mitosis maintain genetic continuity and what happens if errors occur?

Mitosis ensures that daughter cells receive an identical set of chromosomes, which maintains genetic continuity.

Errors in the cell cycle can lead to mutations, abnormal cell function or diseases like cancer

What is the main purpose of meiosis

To produce gametes (sperm and egg) for sexual reproduction.

What are the produces of meiosis?

4 haploid gametes

What are the 8 stages of meiosis

Prophase
Metaphase
Anaphase
Telophase

Cytokinesis

Prophase II
Metaphase II
Anaphase II
Telophase II

Interphase

G1 - cell grows and produces proteins and organelles

synthesis - DNA replication - sister chromatids

G2 - Further growth, prepares machinery for mitosis

Prophase I - meiosis

• Chromatin coils and becomes visible as chromosomes

• Homologous chromosomes pair up.

• A process of crossing over occurs, where segments of genetic material on one homologous chromosome swap with the other. 

• Nuclear envelope / membrane disintegrates. 

• Spindle fibres attach to the centromere of the homologous chromosomes. 

Metaphase I - meiosis

• Homologous chromosome align at the equator of the cell. 

• Independent assortment occurs 

  • The orientation of each homologous chromosome pair is random

  • Maternal and paternal chromosomes assort independently increases genetic variation.

Anaphase I - Meiosis

• Spindle fibres pull the homologous chromosomes apart to opposite poles of the cell 

• Each homologous chromosome still consists of two sister chromatids.

Telophase I - Meiosis

• Homologous chromosomes have fully separated

• Each pole now has one chromosome from each homologous pair

• Cell nuclei are now haploid (n). 

Intercytokinesis - Meiosis

• Interkinesis is the short resting stage between Meiosis I and Meiosis II.

• Occurs after telophase, completing cell division

• Ensures each daughter cell receives organelles and cytoplasm in addition to the nucleus

Prophase II - meiosis

• Chromosomes condense as they may have partially decondensed during cytointerkinesis 

• Each chromosome still consists of two sister chromatids joined at the centromere.

• Spindle fibres attach to the centromere of each chromosome.

Metaphase II - meiosis

• Chromosomes align at the equator of the cell (metaphase plate)

• Spindle fibres pull the chromosomes into alignment

• Chromosomes are arranged so that:

  • Each sister chromatid is attached to spindle fibres from opposite poles

Anaphase II - meiosis

• Spindle fibres pull the sister chromatids apart to opposite poles of the cell 

• Each chromosome now consists of a chromatid. 

Telophase II - meiosis

• sister chromatids are on opposite poles of the cell 

• Each chromosome now consists of a chromatid. 

• Each daughter nuclei are haploid (n). 

• Nuclear membrane reforms and chromosomes decondense into chromatin

Cytokinesis

• Occurs after telophase II, completing cell division. 

• Each daughter nuclei is haploid (n).

• Ensures each daughter cell receives organelles and cytoplasm in addition to the nucleus

How doe the four cellular products of meiosis contribute to sexual reproduction and genetic diversity?

Meiosis produces 4 haploid gametes, each genetically unique. These gametes combine during fertilisation to create a diploid zygote, which contributes to genetic variation in offspring.

Compare and contrast mitosis and meiosis in terms of chromosome arrangement and products.

Feature	Mitosis	Meiosis

Chromosome arrangement

Chromosomes line up individually at metaphase; sister chromatids separate in anaphase.

Homologous chromosomes pair up at metaphase I; homologs separate in anaphase I, then sister chromatids separate in anaphase II.

Number of divisions

1

2

Products

2 diploid, genetically identical daughter cells

4 haploid, genetically unique gametes

Function

Growth, repair, asexual reproduction

Sexual reproduction and genetic diversity

How can plant reproduce?

Can produce sexually or asexually

Name the structures that allow plants to sexually reproduce

stamen (Male organ): Anther, Filament

Carpal (female organ): Ovary, Ovule, stigma, style

Stamen

Produces pollen grains, which contain the male gametes (sperm cells)

Anther

The anther is the part of the stamen that produces and releases pollen

Filament

Supports the anther holding it in position for effective pollination

carpel/Pistil

Contains the ovary, style, and stigma, which produces female gametes and receives pollen for fertilisation.

Ovary

Ovary houses the Ovules, which contains the female gametes

Ovule

produces the female gametes and develops into a seed after fertilisation

Stigma

receives pollen during pollination and often has a sticky surface

Style

Connects the stigma to the ovary and allows the pollen tube to grow towards the ovules

Petals

attracts pollinators

Sepals

protect the flower bud before it opens

receptacle

supports flower head

What is the role of pollen, eggs and seeds in sexual reproduction

Pollen contains male gametes, eggs contain female gametes and seeds develop from fertilised eggs to give rise to new plants

Different between cross pollination and self-pollination

Cross-pollination: pollen from a diff plant, increase genetic diversity, requires pollinators

Self-pollination: same plant, offspring genetically similar to parent, can occurs without pollinators

How do animals reproduce and how do mammals differ?

some animals can produce sexual or asexually, but mammals can only reproduce sexually. Mammals require the fusion of male and female gametes, and they produce genetically unique offspring and it involves internal fertilisation.

What structures allow mammals to sexually reproduce?

Male: Testicles, Sperm duct, Penis

Female: Ovaries, Fallopian tubes, Uterus, Vagina:

Testicles

produces sperk

Sperm duct

Transports sperm from testes to penis

Penis

Delivers sperm into female reproductive tract

Ovaries

produces egg cells

Fallopian tube

transports eggs from ovaries to the uterus

Uterus

site for implantation and development of embryo

Vagina

receives sperm and serves as birth canal

Role of sperm, eggs and zygotes in sexual reproduction

Sperm: Fertilizes egg, contains male gametes

eggs: contains female gametes

zygotes: When the sperm and egg fuse during fertilisation - first cell of a new organism, full set of chromosomes

How do sexual and asexual reproduction help plants and animals survival

Sexual reproduction increases genetic diversity, which allows for evolution and adaptation, ensuring long term survival.

Asexual reproduction produces genetically identical offspring, enables rapid population grow, this ensures short-term survival.

How does sexual reproduction enable the survival of mammals?

Sexual reproduction produces genetically unique offspring which helps mammals adapt to a changing environment, predators, or diseases

Example of sexual reproduction enabling the survival of mammals

Humans sexual reproduction produces offspring with different immune system genes, this help populations resist infections

What are the basic building blocks and structure of DNA

DNA is made up of Nucleotides: which contain Deoxyribose sugar, Phosphate, and a Nitrogenous Base (ATCG)

Arranged in a double helix

Draw and identify the 3 components of nucleotides

Sugar-phosphate Backbone

is a strong covalent bond between the sugar of one nucleotide and the phosphate of the next

Hydrogen bonds

a weak bond between the complementary nitrogenous bases (Adenine Thymine, Cytosine Guanine)

How does variation in nucleotide sequence contribute to variation in genes

The order of the nucleotide determines the genes instruction, as the nucleotides vary, this causes a difference in the protein it’s instructions produces and there trait.

What makes up Chromosomes?

Chromosomes are condenses chromatin, which is made up of DNA and histones

Histones provide support

Structure of chromosomes

A chromosome can have 1 or 2 sister chromatids

If there are 2 sister chromatids then they are connected at the centromere

In most eukaryotic cells they are linear

Genetic info in prokaryotic cells VS eukaryotic cells

Prokaryotic: a single circular DNA molecule, located in the cytoplasm

Eukaryotic: multiple linear chromosomes made of DNA and Histones. Located in the Nucleus

What is the relationship between genes, DNA, chromosomes the nucleus and cells?

DNA is made of genes, which are organised into chromosomes inside the nucleus of eukaryotic cells

How can human karyotypes be analysed to identify sex and chromosome number

Karyotypes are organised in homologous pairs.

The 23rd pair is the allosomes which are the sex chromosomes - XX female, XY male

typical chromosome number is 46

Genetics

the study of genes, inheritance and variation in living organisms

genetic variation

Differences in DNA sequences between individuals which leads to variation in traits

Heredity

passing of traits from one parent to offspring through genes

Genotype

The genetic makeup of an organism

Phenotype

The observable characteristics of an organism resulting from it’s genotype and environment

What is the relationship between genotype and phenotype

e phenotype is the physical expression of the genotype

How does inheritance of traits arise form gene variation and chromosome rearrangement

Inheritance occurs because of different in alleles of a gene. Since the offspring inherits one trait from either parent, which determines their genotype and phenotype. The Rearrangement of Chromosomes during meiosis in processes like crossing over and independent assortment creates a new combination of alleles

How do mutations arise

When there is a spontaneous change in nucleotide bases in DNA it alters the proteins which causes mutation

How is DNA linked to genetic conditions

Since DNA carries genes, a mutation in a gene can alter the protein which can lead to genetic conditions, such as sickle-cell aenaemia

What are alleles

Different variations of the same gene

What are the notations for dominate and recessive traits

dominate: Capital letters

Recessive: lowercase

Dominate traits

only one allele needs to be present for trait to be expressed, homozygous dominate or heterozygous

recessive

Both traits needs to be expressed for trait to be expresses, only homozygous recessive

Autosomal

located on genes 1 - 22

Sex - linked

located on the X or Y chromosome

written with the letter and then the trait above it

Co- dominace

Heterozygous

Both alleles are full expressed equally

eg AB blood type

Where does mitosis occur in humans

Male: testes

Female: ovaries